I've only used Lake Country's 6" and 6.5" pads. However, between the two I like the 6" ones better. They just seem to work better to me. The cutting pad seems to cut slightly better and the polishing pad seems to give a bit smoother of a look. Could just be my imagination.
Even though the 6.5" ones are made for the DA, I find that the velcro is a bit smaller in circumference than the 6" pads, which causes the backing plate to cut into the pad if I don't line it with something (I cut an O-ring out of a Chinet paper plate). The glue is much stronger on the 6.5" pads because it's made for the DA, but I just used shoo goo on one of my 6" pads when the velcro fell off and it works fine now.
Note: even though I'm choosing the 6" pads for the poll, there is no option for the 6.5" pads which are the ones Lake Country actually makes for use with the DA.