Well tough question. Indeed those games 2010~2013 have the best ML in the series.
Now i exclude gameplay. Purely in game modes and content per se.
PES 2010 & PES 2011: For what i want in a manager/career mode 10 and 11 have the deepest possible club managment for a PES game. Budget allocation in 4 sectors, hire staff, youth academy that the regens quality depends on your academy level, depending on money you invested.
The best part of those two games is the trainning mode. IT IS THE BEST OF THE BEST trainning mode possible in PES and even FIFA i would dare to say. No to much for the detail but for the ergonomics of it.
At least in my head, it has all i need when i want to train my players in a MASTER LEAGUE:
1) Train players to aquire new position...CHECK
2) Train players to learn new skills..CHECK
3) Focus trainning points on specific stats you want your player to improve...CHECK
All the above depending always on the level of the trainner you hired, translating in money you spent for a trainning staff.
IE if you have the best coach hire, you can allocate points on NEW POSITION, while in the mean time keep trainning conservative the rest stats. If you have a less expensive coach, you must sacrifice points from some stats...
Honestly the trainning system of the above games,
should be the A and the Ω in any PES game, those level of depth/ergonomics have not reachedn not even in modern ML.
The only difference between 2010 and 2011, is that the menu in 2010 is like a maze, you must dig a lot to find things, while on 2011 almost everything can be spotted on the fly and some other details, like on 2010 the players values/salaries are a little bit more realistic, while on 2011, for no obvious reason, something happened and they cut down all values, like MESSI costing 20million euros and such things. Also they changed trainning schedules. For example in 2010 with a masx level coach you can learn a player a new position in 24 weeks. In 2011 the schedules were doubled, meaning you nw need 48 weeks, almost a whole season.
Also PES 2011 has Fifa Club World cup, after you win the CL, Intercontinental Cup or Club International Cup. There are 3 LATAM teams visible in ML (in vanilla game) Boca, River, Internacional. YOU always play on DECEMBER vs INTERNACIONAL, always.
PES 2011 also has something like my
favourite eleven???, where you can take a team photo shooting i thing.. not sure about this.
PES 2012: The new entry in 2012 content wise, is the addition of Liga Portugal to the existing old PES leagues. CL and EL are the same, i think Libertadores teams are now visible in ML, not playable but you can sign players by them.
The trainning system was completelly scrapped, in comparison to previous games, for no reason it became terrible and ultra shallow. The new feature here the player communication system, from where you can boost your players morale, or disappoint them, or help them with trainning. IE with players communication you can teach them now positions, or new skills, but it feels partly random, not so clear as it was in 2010-2011.
Also other new feature of 2012, is the objectives of the Club owner. He sets you with some mission, like in modern days PES, like win the first match, or use the X/Y player in the first cup match, etc. It states that if you miss the missions of club owner, you may get sacked. BUT I HAVE NEVER reached a point to check what happens if you get sacked?/ GAME OVER? You must change club? NOTHING? Really a mystery.
*IIRC here the FIFA club world cup was imporved to two knockout games, or it has more opponents than only INTERNACIONAL
PES 2013: In 2013 the management content was again watered down, can't blame them, as they focused on other aspects like full BRASILEIRAO, LaLiga full licensed with stadiums. The trainning system was reworked, but is still a rip-off in comparison with 2010/2011. The new system with trainning items and boosting items, gives a new RPG aspect to the game. Most people do not like. Me personally i don't like them, by i tried to use them to make some good out of them, think the new position learning. Also the FIFA Club World cup IIRC was completelly removed, so after winning the CL, there is not something bigger now to aim.
In both 2012 & 2013 the budget allocation and the hiring staff, investment level ,was also watered down, something like from 5 option for hiring staff and 4 options to invest your budget, to 2 options per selection. IE in budget investment, i think it is now invest in FAN CLUB and YOUTH ACADEMY.
Basically as i mentioned before, regarding trainning in Master League, there are 4 basic key points i need to claim a trainning mode perfect in a game:
1) Be able to teach players new positions
2) Be able to teach players new skills/traits (Always of course with respect and relevance, i do not want my GK to learn 1-on-1 finishing, or rabona)
3) Be able to focus my training in specific parts, like a slow player that i can help him imporve his speed, or an old player, help him retain some stamina.
4) Have free trainning in training ground, LIKE PS2era PES games, so i can play a friendly exhibition match, with 11vs11 or less players, or train in scenarios or situations, like 3vs4+GK or 5vs5, etc, etc...
When a trainning mode in ML is like this, it is the best
for me, until today at least.
All in all, in every PES from the above, you miss something , you earn something. But none PES after 2013, even the
""""reworked"""" 
2020 ML, has reached such levels of depth in club management.
I am more into "simulation" type of matches, so maybe PES 2010 is not for me in that regards, but still deciding.. I enjoy PA1, so I also like the reduced pass assistance without it being manual. but in anycase.. Maybe I should've made my original post more clear.. I am not only looking for a gameplay review (which you did excellently, btw), but also other things..
