Probably what you get used to, but I think it would be best to keep them the same for CCW. All mine are decockers. P90DC is an excellent gun, but the P345 is smaller and thinner. Handle and shoot both and get the one you like best. They are both good guns.
i just happen to like the 90 which i believe to be the best dbl action 45 there is on the market.
The 90 is of a proven design with years of service behind it, no mag dis-connect, no key lock. good accuracy, excellent reliability, ability to change grips. a ton of available leather from the years in service. and i trust it to protect the lives of my family and myself with it.
I have no hands-on experience with the 345 other than what i have read about---- so i will let others speak for/against it. if you check around, you may be able to locate a 345 decocker.
I have had a love affair with my P90T for several years now and I could tell stories about it's accuracy and reliability that would bore you stiff, but my youngest son recently bought a P345, and I think I may be ready to change allegiances! (Without getting rid of the P90, of course)
I've got two 345s - a safety and a decocker. I've also owned a couple of 90s. I don't think you can go wrong with either. Just buy which ever one feels the best to you...shooting each would be even better. Decocker versions of the KP345 are still available, both new and used, but they are disappearing fast.
I took two new Rugers to the range last week. One P90DC and one KP345DPR.
Alternating between the two pistols after each four magazines, I put 300 rounds through the pair. Initially, the P345 shot rings around the P90. Toward the end of the session, the P90 was shooting much better than the P345 and the P345 did not seem to change much between the first and last magazine.
The ammo was a mixture of Wolf steel case and Blazer aluminum case ammo--all 230Gr. RN. Not a single failure to feed or fire with either pistol.
Based upon this limited experience, I'd take the P90 over the P345 unless the deciding factors are size and weight.