Export quality in After Effects

I'm going to borrow advice from my friend Dave LaRonde over at CreativeCOW.net. He has answered similar questions so many times this has become known as

Dave's Stock Answer #3:

Don't use AE to compress files for final delivery. The various compressors are there only to make quick 'n dirty files showing a project's progress to producers, clients, the kids, etc. AE is incapable of doing multipass encoding, a crucial feature that greatly improves the image quality of H.264 and MPEG-type files in particular.

Render a high-quality file from AE, and use a different application to do the compression. Popular ones are Adobe Media Encoder, Sorenson Squeeze and Apple's Compressor, which comes bundled with Final Cut Suite. Even compressing in Quicktime Pro is better than compressing in AE.

Making good-looking compressed files is almost as much an art as it is a science. It is NOT straightforward at all.

There's even a forum over at the COW entirely based around compression techniques in video and audio.

So it's up to you if you want to import the AE project into Premiere or just to export a lossless file from AE to use in Premiere. I, like Dave, prefer rendering a lossless file out of Premiere rather than having Premiere link to the AE file. If Premiere is linking to the AE file, it basically launches an instance of After Effects in the background to render it and now you've got two rather RAM-intensive programs running at once.