I've used both maya 4.5 and max studio 4.2, while i feel that maya is the better of the two just because the interface is so much easier for me to use then max.
Jess has the best advice take your time and try them all out before you make a purchase you might regret later on.
Also i actually ended up buying Truespace 6.6, instead of maya or max for the simple fact that Truespace is 1/4th the price, the whole package for truespace, with fx pack, ray pack, de pack, anipack, and gamepack only cost me around 1,200 vs 5,000 for maya and 3,500 for max.
Since i don't plan on making cash from any of the programs/games im working on, i couldn't see spending that much money for the better modeler's since this is just a hobby that i do on my spare time.