I foun d similar results as you know - I had an issue with CCDStack and PI wanting to only register the hot and cold pixels and ignore the stars - the big issue for me is, because I use OSC and MUST debayer peior to registration, of course the algorithms are going to like saturated colour pixels more than white.
Anyway, I found a way in CCDStack to now get a result as TIGHT as PI, and in far less time. I had to register and then register the lanzcos/sinc36 twice in CCDStack until there was NO discernable image shift on blink.
PI did the same in the end for me too, but the process takes a LOT longer for the same end result (there is NO star size difference in the end when you overlay each stack on each other).
So, I am still undecided if to use PI or CCDStack despite my PI victory last week
PI REALLY needs to get more friendly with their output scripts too - they need to have an EASILY found "Save Scaled Data" function, not squirreled away in technospeak
. PS REAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAALY hates PI's TIFFS - the level histogram is impossible to work with