I use to have the same rule: slower = better because of less errors. All disc burns have errors, all disc readers have error correction built in; you just don't want to push the envelope!
Now however I had modified my slower = better to slower = better. In other word, do not burn at the fastest rate allowed, but don't burn at the slowest. Today's media is made to burn at higher speeds. Burning at too slow a speed can create the same errors we were trying to avoid. What is that middle of the road speed? Depends on the media/burning. If my options are 4x, 8x, 16x- I would choose 8x. If my options are 2x, 4x, 8x, I would choose 4x. If my options are 1x or 2x, I would choose 1x (not the fastest happens to be the slowest).
Mike