Yes, the slower the burning speed the less likely it will be that there will be errors. However as far as I know, you shouldn't burn too slowly. For example if you have a dvd that supports 16x speed. You shouldn't try and burn using 2x or 4x. You should pick a medium speed like 8x or 12x.
Thats just my understanding of it though.
Burning at a slower speed doesn't make it a better quality burn, however burning at a faster speed can allow for more errors I think.