Sorry about the vague subject.

I have some old MP4 files progressive ( avc / aac ).
I still need to selectively take some parts, apply some effects and
then render to a format/codec that I can use later for additional editing
or stand alone playback on a computer.
Ideally, either the same format as the original or something else like MPEG2.
(DV/AVI would be too big of a file.)

So, would it be best to render to AVC in terms of what quality I can hope for?
Would one be better than the other ?

I'm sure this seems totally bogus with regard to generational loss,
but that's what I need.

Thanks for your help.

Mike