You may have read some of this already since I did some cut & paste from a post I made on another forum...
When our local sporting goods store received a shipment of both the Colt M4 22 rifle along with it's "tactical" version, the Ruger SR22 and the S&W M&P 15-22 rifles early last month I did some hands on time with the guns. Later, after doing some checking around the internet for reviews of both the S&W and Colt (I couldn't find anything on the Ruger but I'll guess it's as reliable as any Ruger 10/22), I bought the S&W. FYI, I liked the Colt Tactical model of the .22 and considered buying it. It was almost exactly the same as the S&W but metal. However, it was almost $200 more than the 15-22 and at least a pound heavier due to it's metal construction.
There are those who will argue the point, but I personally prefer the S&W's lighter weight polymer construction vs. the all metal of the Colt. While there are many people who like their guns made of only metal and wood (I do myself in most cases), I think a polymer frame/stock is a good choice for an all purpose & all weather gun, especially a .22. It's usually lighter (weight is good for recoil control but a .22 has no recoil), won't rust, is much less likely to break or warp, is usually cheaper to make and can be molded into almost any shape. Several people suggested I get the basic 10/22 and "trick" it out and I considered it. However, between the cost of a new gun, an aftermarket stock and other parts that met my requirements, it would have cost as much as the S&W by the time I'd purchased everything separately, quite possibly more. The S&W's standard factory rails and the fact that it was $125-$175 cheaper than the Ruger SR and Colt M4 were another big selling factor. The 15-22 has a MSRP at the S&W site of $500 but I walked out the door with my M&P for $450. Something else that was nice for me is I already had a lot of extra parts from an AR that I'd sold a number of years ago. So along with some rail covers I had sitting around, I was able to add a carry handle and vertical grip at no extra cost.
I've shot about 250 rds during my two trips to the range with the M&P. It was just as accurate and reliable as my old Ruger 10/22 and I'm able to do a lot more with it as far as customizing than I ever could with my 10/22. FYI I'd still have that 10/22, which I got back in the 80's, but it was stolen during a burglary about 15 years ago when I lived in New Orleans. Anyway, I was hitting cola cans at 75+ yards and my youngest son (10 y/0) was putting most shots into a 6" circle with the iron sights at 50 yds with the gun after a few practice shots and we were both having a blast... literally!
To tell the truth, this gun is just plain FUN
to shoot! At 5 lbs the S&W is light but with it shootng the mild .22 LR, there's no recoil to speak of and it's nice not having to deal with recoil when my kids shoot it. There are also no non-functioning knobs or buttons (a fake forward assist for example) like there are on some of the other AR clones. You can swap out the M&P's trigger assembly with any standard AR match trigger if you feel the need along with the stocks while the rails accept Weaver based and picatinny accessories. It will also accept most aftermarket pistol grips as per S&W. According to several different reviews I read the barrels are high quality match grade" and made by Thompson-Center so it should be capable of very good accuracy. While none of these guns are exactly true AR inside, the Colt and S&W are close enough that those who have a "real" AR will be familiar with it's parts and functions. All the external controls and switches are in the right place as well. In addition, with the adjustable stock and it's light weight, my wife & kids can shoot it just as easily as me and my kids won't outgrow it like they have several youth model guns.
As I said, I considered both the Colt and the S&W and for my purposes the S&W M&P 15-22 was the way to go. OTOH, if you want something closer to the classic M4/M16 in looks and feel or simply like metal over polymer you may want the Colt. The Ruger SR is another good polymer choice but it's as expensive as the Colt's. If you want someting less expensive and more easily available than either the Colt or S&W, get a Ruger 10/22 or one of the other more traditional .22's available at most gun and sporting goods stores. There will be those that prefer one over the other, but so far I'm VERY
happy with my new S&W rifle and would recommend it to anyone who asks. This is a photo of my gun with the extra's I mentioned earlier...