I was preferred plus, then gold, and am now preferred plus again. On paper, the benefits are the same (except for the 50% point bonus for Gold). In my experience, I was much more likely to get upgraded to a preferred room as a Gold than as preferred plus. It may have been differences between the hotels I was staying at (the extent of participation does seem to vary quite a bit by hotel), but I can't imagine the person at the front desk saying to me, "Oh, Mr. Goodman, I see you're a Preferred Plus Guest...we've got an upgraded room on a preferred floor for you," but I'll keep my fingers crossed.

I've never been given late check-out with either status.