I've owned a few new and a few used ones. My fist S&W was a used 6" Model 66 I bought in the mid 80s. My first new S&W was a 2 1/2" Model 19 I got in the late 80s. Both are long gone, replaced by some other revolver or rifle I "needed" at the time. My most recent was a Model 340 that I got new at a local dealer his past year.
I don't really prefer new or used, as long as I can find a model that will fill a perceived need or want, that's all that matters. I really like S&W's warranty and have had to use it on a couple of new revolvers. And they were kind enough to extend this to a couple of used revolvers that had issues also. I also gladly paid, very little, for a repair on a used 629. No MIM or other scarey stuff in that one, but it broke anyways. I did manage to find a used 2 1/2" Model 19 to replace the sorely missed one I never should have sold.....