with ae you'd like to render to an uncompressed/lossless codec, then compress at the next stage in the workflow.
if you r next stage in an nle, like vegas, render uncompressed avi or lossless mov, and import that into vegas.
if you just wanted to create an mp4 or another low bandwidth format, take you uncompressed/lossless file to a compression app like adobe's media encoder (it should have come with cs4+) or the compression utility of your choice (mpeg streamclip makes a pretty good mp4).
if you need to render to a compressed file from ae, i'd recommend quicktime photo-jpeg at a higher quality setting (85 to 95+, 75 at the lowest). but photo-jpeg is still a fairly high-bandwidth codec compared to mpeg-2 and mpeg-4 based codecs.