nuendo's great, but why not just get sx3 if you don't need the post features? sounds like a no brainer to me...
if you're trying to get a feel for these apps, why not pick up a video tutorial of each one to see them in action? the ask video sx3 series is very good - the third disc really shows off cubase's advanced features:
http://www.askvideo.com/index.php
cool school puts out a pretty good dp tutorial:
http://www.courseptr.com/ptr_detail....9200%2D167%2DX