Is sound quality better on a 12" or a 10"?
The sound quality is the same on both dub plate formats, but the wider the circumference of the groove, the better the resolution of the recording. This means that there is a slight reduction in sound quality towards the end of any lathe-cut vinyl disc. Most of the time, this is not noticeable, but because 12 inches are wider, they have more space to record before reaching the center of the disc, and so (for a while at least) they will sound better than a 10 inch.
Also, because there is more space, its often possible to cut the same track louder on a 12 inch than on a 10 inch. Having said that, provided the tracks aren't over 6 or 7 minutes, its possible to get really nice, loud recordings on ten inch too!