You're correct that the dirt that Kleenbore primers leave isn't harmful but to get rid ofthat dirt is supposed to be the reason to pay the extra money for them ( $8.85 per box , at the only place I can find them near me, compaired to $2.75 a box for small rifle primers ). There is less 777 crud ring with Kleenbores but there is even less, in my Omega, with the small rifle primers. There is virtually no primer pocket area fouling.
I use CCI Mag small rifle primers and they are fairly hot. I think I will use your reasoning and hunt with the CCIs and carry a hot Federal 209 primer for a back-up, just in case.
I would like to try the new Winchester 777/209 primers when they are ever available in my area.