Replying to Manfrotto 502 vs. 504

Hey M&A I'm going to be upgrading my tripod setup.  Head and legs, the whole deal.  I am looking at either the 502 or the 504.  I was wondering if anyone had been able to work with either or these setups and preferably both.  I have a few questions about them before buying one.  It's always nice to save a few hundred bucks if possible.

-It appears the 504 is bigger but is the difference worth noting?  They look pretty similar in size but can't really tell.
-Any of the Manfrotto heads with the 75mm ball can be leveled without manipulating the tripod legs correct?
-How easy is it to set the counterbalance on the 502?  I know the 504 has the 4 stop knob on the right side which looks pretty sick.  Does the 502 have the same feature?  I would assume so but wanted clarification.

Thanks guys!