I personally dont like being in the premiership becasue i dont like it as much as the coca cola leagues, but coca cola league 1 is the best by far as all the teams are so equal in abililty, apart from leeds, that it makes for an exciting season no matter who you are!
i must league 1 aswell as i'm a luton town supporter and it makes it more of a challange as there is hardly any players in the squad. i also like playing in the confrence as the teams are nearly so alike which makes it really intresting.
MLS. Right now it's a little too buggy to play in FM. But the funky player rules and the relative parity among teams makes it fun to play.
Also like the Irish Premier Division and the lower levels of the English structure. Back in FM07, I also played in the top Russian league for two seasons, which was quite interesting.