I have a 930 spx and would definitely trust my life to it. Mine has been totally reliable, even with mixing light target loads and full power buckshot back and forth. I did this a few times with a full tube of all sort of random loads and that was proof enough for me. IMO, if it is for someone who doesn't practice much, a semi has a couple of advantages.
First of all, it can't be short stroked. As I run this in 3 gun matches, I have seen pumps short stroked and even completely jammed by people competing. Yes, this can be trained around, but I doubt I could get my wife to put in that sort of training.
Second, on the occassions where you can get an infrequent shooter out to practice, the semi action is much softer shooting. This was actually a big decider for me when I selected the 930. It is very nice to shoot even with full power loads. That said, I do stick to 2 3/4 loads as I don't see reaching out very far with this gun.
That said, if you can get the wife to put in the practice with the 500, then having two of the same gun probably makes more sense, but for the reasons I stated above, the 930 worked better for me.