The case is as already mentioned, that Fifa Manager is not really realistic, you don't have many possibilities. But after spending lots of years playing Anstoss (2,3), which are ugly, but realistic manager games by a German producer, the decent look of Fifa Manager is a great alternative. If the players look the right way with photos'n'stuff and you can watch the game, it makes me get closer to the team, it feels more like reality to me, since FootballManager (I tested it) sometimes optically reminded me of Microsoft Excel.
Fifa Manager '06 is almost awfully easy to play with Werder Bremen. That kinda sucked. Another thing was that after I reached a high level of fitness with my team, it never went down again, and I did not train that much of it anymore. I was slighty irritated by that.
But after I'm done with PES6 for 1st, I'll probably return to Fifa Manager again.