I prefer about a 10" tree over a larger one. The bigger ones seem to slow their growth in later years, and I've run into more problems with rot and wind shakes in the big ones too. My ideal, is a nice 8-10" diameter tree growing off a cut stump in a hedge row. These grow up fast because they have an established root system feeding them, and they grow with few limbs because they are partially shaded by stuff growing around them. More often than not, these things are clean and have nice growth rings. By the way, around here a healthy 8"-diameter tree is around 15 years old and has growth rings around 1/8" or better.
The other place I have found good trees, is in the woods where a tree has a lot of shade and has to grow up to find light. The ones out in the open, tend to grow really twisty and bushy.