Choppy

Hello, I am currently animating my fifth or sixth big animation with TB Studio 5 and whenever I export it on default settings, there is virtually no choppiness but the quality goes down greatly when I re-save it in my editor, Sony Vegas Movie Studio Platinum 9… so then I go into custom options and I make the size bigger, one of the “HD Quality” options and I save it and the camera movements and animation itself is endlessly choppy and while it is sharp, it takes away from the animation itself greatly. Anyone know of any better options to save it under? Is there some magic code I am missing? Thanks.
-James