I use DRC pads, especially white and green; but they are rotary pads, with a hole in the center for minimizing swirls, so they say, but I never used on the 3401, only on the PE14. The DRC on a rotary works pretty well. The problem is the backing plate, you need a DRC backing plate, since the 5 inches is too big and 4 inches is too small. But I use on a 5 plate anyway, but the fitting is not perfect.
I started using DRC mainly for the price, people in my country didn't like it, so it went on a huge sale and I bought around 10 pieces. But I got along with it very well, and indeed it seems to minimize rotary swirls. But never used for finishing, though.
I would get 6.5 hybrids on a Rupes. And forget about using DRC for finishing. I also think that finishing with the Flex is a better choice than finishing with a Rupes.
The hybrid pad line is best line of pads I came across, if I could I would buy a truckload of it.