I honestly see little to no difference between teams (on World Class, tweaked sliders).
I've tried experimenting with setting player run sliders for CPU high or very low (0 !!) and experimenting with line height but honestly teams like Juve/Man C/Man U/Real/Bayern play a very generic 'possession' game and I see virtually no player/team individuality.
What team personality and what traits are you seeing? I remember one of the previous FIFA's had rather lame 'team traits' but it was in a very limited state and was implemented poorly. I wonder if the code the guys at soccergaming are seeing is just vestige from earlier titles. I did some ini editing for FIFA over the years and the last couple of years ini editing had very minimal changes to gameplay, and the only way to consistently change CPU behavior was via large DB edits.
I'm not trying to troll, although I have a preference in PES over the years I've generally got FIFA to play online with friends and if I was 100% satisfied with PES 2014 I wouldn't have bought FIFA
I don't have any particular 'brand loyalty' one way or the other and am having fun with FIFA (at least until some of the bigger PES mods come out).