Thanks for the responses!
Space, particularly on the iTouch, is the biggest issue. I can only fit 20 or so albums on my 16G Touch along with apps and movie/tv shows. I think I'll copy my AIFFs to AAC 256k and listen in all environments to see if i can hear a difference.
JoelV - good point with headphones, as I listen through my Audio Technica ATH-AD700's through all sources listed above.
If I can't hear the difference, I guess my dilemma goes to Mb9061's point - do I run the risk of re-ripping in the future? Of course, if I rip AIFF, move those to a portable HD and keep the AAC files on the macbook/iTouch I also run the risk of hooking up the HD in a few years to realize that the music is gone anyway....