To maintain quality, minimize compression. Some Quicktime options are:
– Animation codec, 100% or slightly less
– Uncompressed 8-bit 4:2:2
– Photo-JPEG
… but with less compression, you have higher quality, but are less likely to play the movie back without skipping.
So. Once you render these titles, what do you want to do with them? Play them back as a final deliverable (playability important), or import them into another application for further processing (quality important)?