I have a Mossberg 930 SPX, and I like it. If Mesa Tactical would get off their asses and bring an Urbino stock to market for it like they've been promising to do for about a year, I'd like it even more. As it is now, the LOP is pretty long, probably too long if your wife is short. My girlfriend is 5'0", and there's no way she could use it. For more money, you can get a little bit better (I'm told) shotgun in the form of FN Herstal's police shotgun. For more money still, you can get the Benelli M4, a semi-auto shotgun so good the Marine Corps is replacing their Mossberg 500s with it. I haven't handled one, but the Benelli is the unquestioned best semi-auto shotgun on the market. I read a lot before I bought my Mossy, and the only negative thing anyone ever says about the Benelli is that it costs an arm and a leg. Is the extra money worth it? I don't know, my Mossberg runs pretty good, and cost about a third of what the Benelli would cost.
Here's the negatives that I don't like about my Mossberg: the parkerization is pretty thin on the barrel, if you don't wipe off a fingerprint on the barrel, you will have an orange spot. So far they've all come right off with a quick CLP wipe-down, but it's a problem, nonetheless. The other thing is that Mossberg failed miserably with their extended magazine tube. It just hangs out there like a lonely ding-dong, and imho needs a barrel clamp. I got the one from Nordic Components, which looks good, but you have to be careful with it. If you tighten the screws down too much, the clamp can pinch the magazine tube (which I also replaced with the Nordic Components tube in hopes of solving that problem) and can bind the follower.
On the bright side, as long as the magazine clamp isn't tightened down too much, I haven't had any malfunctions with it. It's much cheaper than the other two, which may or may not be a factor for you. If I had it to do over again, I'd save more pennies until I could afford the Benelli. $1800 is a ridiculous amount to spend on a shotgun, but like I said above, the only thing anyone seems to be able to find to bitch about is the price. Buy once, cry once, and all that.
As far as using a semi-auto for HD goes, I'm fully in favor. The semi-autos that are on the market today are much, much more reliable than were available a few years ago, and I think they're plenty good for home defense. Sure, pump guns will cycle anything and everything, and they're much simpler than a semi-auto, but a little practice will close the simplicity gap. Here's a little final food for thought about pump vs. autoloader: An autoloader does have a higher chance of a malfunction than a good pump, but the odds of that happening on any given shot are pretty doggone low, and they stay the same whether you're sighting in slugs off the bench, busting clays, or staring into the bloodshot eyes of your friendly neighborhood meth head. A pump will never malfunction at the range, but are you certain you'll FULLY cycle the action under stress? Although the odds of a malfunction with a pump are lower, they go way, way up under stress because they require conscious operator action to cycle the action.