4-2-4 for me
I tried all the others after getting brutalized by Gianni, Andy, Steve and Chris... but having the wingers in handy places and knowing where my number 5 SHOULD be is nice and the number 6 can block out a lot of the key passes that are the main source for routine goals. I guess it's for me just because I know where all the players should be at any given time, altho they're not always (or even often!) where you'd actually like them to be
I also liked falcon cause it was similar to 4-2-4 but has the number 5 set a bit deeper for extra cover, but I found the wingers to be a little too far up pitch for my liking.
after that, 5-3-2 is nice if you want a little more security at the back and like to lob a bit more... right Steve?!
so yeah... i just went with what I felt most comfortable with rather than trying to adapt my style of play, might not be right but feels right... if that makes sense
as for ones not to use... i found 4-3-3 and blitz to be almost suicidal