I'm looking to get an SD9 or 40 just for home defense. I haven't been able to find one to try out, but everyone I talk to says get an M&P instead. Is the SD really that bad or is the M&P just that good. I've shot the M&P and it's really nice but I like the feel and price of the SD.
I don't own an SD or an M&P so take these observations for what they are worth.
1. The M&P is more lefty-friendly. If you're a lefty that's probably a big deal. If you're right-handed, maybe it doesn't matter at all.
2. The M&P is more accommodating to a variety of hand sizes. If the SD fits your hands, then it's great. But if you have hands that place you at either end of the spectrum size-wise, then the M&P might be a better choice.
3. Right now there is a better availability of blue guns, training barrels, holsters, lasers, a subcaliber version (.22 LR M&P), remotes for lights, etc, for the M&P than for the SD line. My guess is that difference will continue for the forseeable future. If these things matter to you, then the M&P may be a better choice. If they aren't very important to you, then the SD is fine for you.
4. The M&P line is available in a greater variety of configurations. If you want a .45, then the M&P is a better choice. Want a thumb safety? Go with the M&P. Want a Compact version to go along with a full-size or a 5" gun? get the M&P. Don't care about any of that? It's a wash.
5. Money a big factor in the decision? The SD is cheaper.
6. My educated guess is that a .40 M&P would last longer under heavy use than an SD40. The M&P was designed from the ground up as a .40. My guess is that the SD (like the Glocks) is basically a gun designed as a 9mm and then modified a bit to function as a .40. Glocks in 9mm have a reputation for greater longevity than .40 Glocks. My guess is that an SD9 will last about as long as a 9mm M&P; this is just a guess. I also expect an average SD9 to outlast an average SD40. We won't know for sure for a few years. If any of this is true, and you want a .40 that you'll shoot a lot, get the M&P. Want a 9mm? the SD is probably just fine.