Why do I only have these formats in my output? Where's Windows Media Format?
WMV is not lossless. As all distribution formats, it's highly compressed.
An AVI file can of course be uncompressed, but on the Mac version of AE, AVI is only available as a Quicktime export component (ie, it appears in File > Export) which is really not a recommended path to export video files from After Effects. Same for Flip4Mac. So, yes, exporting a lossless Quicktime file and feeding that to an encoding application is a good idea.
Adolfo Rozenfeld · Adobe