Most of my Commander time in the late 80's - early 90's was in 500A's, but I did get some seat time in some -B's and I flew a 680F a couple of times. One of the 500A's I flew the most had >2400 SMOH on both engines at the time, and I flew a bunch of time in a 310-I that had the IO470's too. Both of those examples kept running and "coming back for more". Because of that one high timer I flew a lot and all that 310 time, I'm personally a fan of the IO470's, but am not saying it is better than the Lycoming 540 line, just speaking of personal experience.
With that said, the time I had in 500B's was a pleasure with the increased power quite noticeable, and I especially enjoyed the Ray Jay's on one of them I flew a handful of times.
Like Adam mentioned, I will offer up that I did feel the 500A was a bit underpowered, the biggest noticeable effect was that it translated into slower cruise speed, while it still jumped off of runways just fine IMHO.
If I had a choice and the cost was equal, would I take a B or an S over an A? Hell yes. In that regard I'm with Bruce for sure.