Winning Eleven IS Pro Evo, it's the same game!
I'm a Pro Evo fan, by a long way.. Yes the licences in Fifa are good, but you can modify the teams (I did it a couple of years ago with the full West Ham team.. took me several hours) and even buy memory cards off the net with full teams on them. So that doesn't matter so much.
As far as gameplay is concerned Pro Evo is miles in front. Fifa is totally unrealistic but with Pro Evo, those occasions where you manage to score a cracker volley or diving header really make it worthwhile. In Fifa you do it every time, but in Pro Evo you feel like you really earned it, and a spectacular goal is genuinely spectacular because of its realistic level of difficulty. And you need to use tactics more rather than just have a single guy take on the whole team and score - the tactics are far more realistic.
So it's easily Pro Evo for me - I haven't even bought a Fifa game since about 2000.