"whats the best quality format to render video "

Not being a smart a__, really, but kind of asking how high is high? As in the print world, start with your destination and work backwards - archiving the source as desired. If it's gonna be DVD/SVCD, then mpg2 is effectively mandatory for now (possibly DiVX, mpg4, &/or wmv 9 in the future). If it's going to be streaming web video, or if playback is going to be only via PC, you'll often get better results with one of the PC-Centric codecs like winmedia, real, DiVX, Xvid, mpg4, Q/Time etc... Artifacts in the finished video can usually be eliminated by upping the bandwidth, shouldn't be too much of a prob. now days with vbr, and in problem situations can sometimes be eliminated through playing with the video beforehand as well as encoder settings.

With winmedia and other more PC formats, sometimes softening the quality level a bit (adding smoothing) helps, sometimes adding or leaving in a bit of noise, sometimes playing with lightness. With most all types of compression, use of vbr allows more bandwidth when needed, but be careful the minimum doesn't drop too low or you'll get artifacts during low motion, simpler scenes. Sometimes filtering before rendering, &/or IVT, Deinterlace, slight blur etc. helps.