I have the alum roller handle on a 550 & 650, and the plastic roller handle on a 550. Both type roller handles are more comfortable than the standard ball handle, IMHO. And, I used the ball handle with a sock over it for 10+ years, because I thought the Dillon roller handles were "gimmicks" and too expensive.
Since getting my first roller handle when purchasing a used 550 that came with the roller handle, I've become a convert. My first roller handle was the plastic style. About a year later, I had an opportunity to purchase an alum roller handle for about half price, and decided to give it a try.
For me, the alum roller handle is more comfortable than the plastic roller handle, because the alum roller handle has a completely round OD, while the plastic roller handle, while mostly round, seems to have a "flat" on it. This flat makes it a little less comfortable for prolonged use.
On my 550's it's more of a toss-up as to which works better, because you have to let go of the handle each time, to set a new case in the shellplate. With the 650, you never let go of the handle, and the completely round alum handle is very comfortable to grip for longer periods.