Any kid with the internet or an ounce of mechanical prowess can build a bomb in his basement that will kill 200 people, so I don't really see guns as being such a big problem.
The bad guys will get them whether they are legal or not, so you might as well grant access to vetted individuals.
That said, think about this: the point of a SMG is to be tiny, and fire a large amount of bullets fast. Instead of using a big rifle round for knockdown power they shoot many small caliber pistol rounds. So, why would you get a semi-automatic SMG? Might as well own a handgun.
But, if you're looking into a small pistol-caliber rifle, I would suggest you look at the Hi-Point carbine. They cost about $100 new, come in 9mm, .40S&W and .45ACP and are rock-solid and reasonably accurate. For concealed carry I would say a .40 S&W or .357SiG is the way to go.
At work I carry a Sig P229 in .357 SIG, a S&W M&P in .357 SIG, and an M240. The P229 is the standard carry sidearm for us and we have had very good luck with it.