Kinda difficult as I haven't played PE4 for such a long time!
But comparitavely to WE8LE:
Graphics: Better. More animation in players, you should see how they go to ground now - nice. No crowds in the stands while in open play - I think this is to prevent slow down ( I used to to turn off the crowds in WE8LE anyway - so it is better this way because atleast you can still HEAR them even if you can't see them).
Sound: Seems much the same to me
Gameplay:
1. Goalkeepers - Not as good, but more realistic. They can pull off some incredible saves, but other times will let a piledriver go past them about a foot away. Sometimes you can score, and the keeper will be rooted to the spot. You can beat them at the near post more readily too, (I think this enhances the game as give you more options, you don't HAVE to shoot at the far post every time).
I get the feeling that the keeper can be off-sighted, and makes it easier to score through a ruckus of players (if you don't hit a player that is).
A VERY, VERY annoying this is that they have made them rediculously quick. This only becomes apparent when you try to take the ball around them. I had samuel Eto'o round the keeper, only for the keeper to turn, run, bend over, and PICK UP the ball (I mean, not even DIVE onto it - PICK IT UP!!!!) before Eto'o (ETO'O!!!) could reach it even though he was running in THAT direction. Stupid if you ask me. This has happened on quite a few occaisions. Don't remember it from WE8LE.
A nice ?new? thing is (as it is in we9) that sometimes you can round the keeper, the keeper misjudges, and takes the strikers legs. Red card, penalty. Beautiful. I can't EVER remember the keeper being sent off (in the box) in WE8LE.
Also, the keeper can throw the ball to the half-way line now. Lovely. However, you do have to be careful, sometimes, you want to launch it to one of your wingers with a throw, but he ends up rolling it out. Happened to me in a league we were doing, cost me the league as Rooney robbed my defender... the rest is history.
I have noticed however, that the keeper can sometimes freeze to buttons. I mean, You can be pressing buttons to make him kick or throw it, but he just stands there. Luckily, (i think this is a new thing since WE8LE) the new feature where the keeper auto-kicks it after a few seconds sorts that out. I like this new auto-kick feature. My brother used to cheat by letting time tick away while the keeper held it in his arms. Bastard.
Defence: You'll have to re-learn defending. Period.
Gone are the days where you hold X and wait for Stam or Nesta to rob the opposition forward. No sir. Not anymore. Do that if you want to give away a freekick every 10 seconds. Now you have to anticipate the runners direction, or poredict where the pass is going, and step in between. The timing of the X-button press is now crucial to winning the ball fairly. This may seem like an improvement, and certainly to some levels it is. However, although the idea is good, "make defending a challenge, and hence more rewarding" but it has been poorly implemented. I say this because you aren't really "punished" for poorly timed tackles. In fact, it is advantagous to hold X and let your defender foul. This is because you NEVER get booked. Let me put a scenario to you. Shevchenko is running side by side with your defender. Your never gonna catch him. In the old game you had 2 options. Either you let him go and pray your keeper saves it, or you bring him down, and get sent off. These were your only options because you knew if you tried an "x" tackle, you'd bounce off, and he'd race clear with more time to choose a shot. Not any more, Nope. Now you just push X, therbeby fouling him. And you don't have to worry, bcause even if you fall, and he carries on clear, the absolutely USELESS advantage system will stop play 90% of the time. So, punished for the foul. No sir. No red card for a professional foul, hell not even a yellow. NOW, you've got 10 plyers between him and the goal. A nice big wall and a freekick system that makes it quite difficult to score. Yep, now a freekick outside the area is nolonger a 70% chance of scoring if you've got a decent freekick taker. More like 10% now.
This whole new tackling system has ruined the game from that perspective. The only thing it has done, is make the game stop-start. Oh yeah, you also give away penalties for breathing on a striker now. My advice - NEVER push X in the area. You are MUCH safer doing a slide tackle - but the best thing to do is to get between the striker and goal, and BLOCK.
Midfield: Not much changed here really. A few tweaks, but all in all it's the same game. I do think it is slightly more difficult to make a good lofted hrough ball, Goal keepers also seem to be more alert to the danger of a through ball. Headers are also more animated, and you can give fouls for pushing and tussling in the air (nice touch). But the main gist stays the same. There is a new thing where you can hold the x for longer, and your player will pass it to a player who is NOT the closest to you in that direction - improves the game.
One thing I have noticed is that control has been messed up a little. Far too often the player will knock the ball too far infront on recieving the ball and lose possession. Also, control of the players seems to dissapear on occaision, when they decided to sprint with the ball straight out of play, even the you are pressing the d-pad in the opposite direction and are not holding the L1 button at all. There are a lot more stray passes, but this is not necessarily a bad thing. It just means you have to be more carefull when passing rather than push x and be fairly confident it will end up with a team member. You seem to get less time on the ball, and turning and passing, hell - everything just seems longer to perform. (This has been improved in PE5 over WE9). I get the feeling the turning arc of the players is much bigger too,
Attack: Again, with the new defene sytem, you do have to change the style of play a little. You can nolonger just run "thorugh" players if you have a forward with high pace and power ratings (eg shevchenko) because they are now fouled and no advantage is played instead of defenders bouncing off them. So now, you do have to pass or rely on very good dribbling skills, or just plain old luck and hope the ref plays advantage.
Shooting looks great. High powered shots that goalkeeprs can save. However, I do find the shooting sysem a little inconsistent. I mean, you can load a shot to the same place in the power meter, and on occaisions he will HAMMER it, and on others, the ball will trickle from his feet. Whether this is just me, or the game, I'm not sure.
Also, the R2 system has changed a little. Admittedly, I never really mastered this in the first place, and my timing is still way off. I think, if you hit the R2 before you release the shot, then your player will side-foot a measured shot - can be a beautiful curled shot into the corner - looks very good. If you hit R2 just as your player is making contact with the ball on shooting, he will hit the ball very hard. Now, somewhere in the timing ( i don't know exactly when) hiting R2 also does a new fake shot. I've been runnning with Angel of Villa, tried to hit a piledriver (obviously mistimed) and he faked a shot, causing the defender and keeper to commit, and then hit a shot into the far corner of the net. Absolutely beautiful. Very good, the new system, but my only complaint is that two very different actions can result from mistiming very slightly. The diffference between a curled shot and a piledriver is VERY obvious, and can be quite annoying when while you are trying to hit the ball HARD from 30 yrds, a millisecond mistiming a=can result in a tame, curled shot from 30 yrds that just rolls wide.
There are some new skills too. There is a drag back which I LOVE. You're running with the ball, you stop, hold R2, and as the defender comes to make a challenge, you push the d-pad in the direction opposite which you are facing, and he drages the ball back, leavs the defender standing, and off he goes. Absolutely beautiful. Also holding r1 and r2 and tapping l1 three times knocks the ball round once side of the defender, and you run round the other to get the ball. VERY difficult to do, but feels great when you pull it off.
Chipping has been changed too. Harder to score in my opinion, but I'm not used to the system yet - more practice before I can make a true judgement on this.
Conclusion:
As always - there have been improvements over the previous installments of the game. There are aspects that have been changed that you initially wish hadn't been touched, but as always, you get used to them, and realise wit time that the change is for the good.
The game is vastly improved over the previous installment in my opinion, and from what I have seen so far, PE5 has improved on some of the niggles that I saw in WE9. I haven't played it much yet, so whether I keep that opinion is yet to be seen.
I hope this is helpful.