Everyone has their preference, of course. I used to prefer RWS #1075 caps....when I could get them. These days I use the Remington #10 caps on the revolvers, and Remington #11 caps on the Plains Pistol and Trade rifle. The #10's fit all my revolvers, no pinching or squeezing required (and resulting potential for a chainfire) and they seem to "frag" less than CCI caps.....which is important to Colt shooters, as the Colt repros seem to like cap-swallowing and the resulting jams.
These are carried by Bass Pro Shops in-stock, and I believe, most Cabela's