No, no, No, NO!
You got it all wrong! If you want a fighting revolver, you need to have a S&W .50. That is, if you don't want a .50 Desert Eagle.
Seriously - - your question was, I believe,
For a fighting revolver would the SW 66 4", 66 2-1/2" or the Performance Center 3" V8 627 be best?
Of those choices, and presuming you want to carry it concealed, My choice is the 4" M66 with small stocks in good holster mated to a decently wide and thick belt. If you can wear an IWB holster or a belly band, so much the better. The 4" K frame is one of the world's great all around revolvers - - Small and light enough (barely) for concealment and everyday carry, with enough heft to be controlable with some very serious loads, and enough barrel to develop good velocity with them.
In my personal experience, the 2.5" version is useful, really, mainly for pocket use, but too heavy for most such applications. That, and for a horizontal shoulder holster. There's no real advantage for it in a belt holster, especially as there's not enough barrel to press against the hip and keep the butt tucked against your body.
Same comments apply to the 627, about concealment. I've carried an N-frame concealed and I find it too heavy and too bulky for continuous,
comfortable carry. Again, the exception might be in a shoulder holster.
One man's opinion, backed by 35+ years of concealed carry. YMMV.
Best,
Johnny