Well, I've done both but I can't tell you which works better because neither beer is finished. I think the preference would be to use the primary because as David said the yeast in the secondary is much less flocculent. I used the secondary because I wanted that strain of yeast and the only place I had some was in the secondary. I had a long lag time, but it did take off. I'm going to rack it to secondary this weekend. In howtobrew.com Palmer says you can use the secondary, that it is easier because it's cleaner, but to be careful about going too many generations because you're developing a much less flocculent strain.