iphone movie players?

hey,

last time im watching a lot of movies on my iphone befor going to bed, school, traveling etc etc,

but, when i download them i need to convert them to mp4. well im lazy and saw there are many apps that play all kind of formats, so my question is which one is the best? not gonna wast all my money on buying them all xD

downloaded yxplayer but its pretty laggy :/

xoxxoo