I was in your exact shoes two weekends ago at the Fitchburg gun show. I knew I was going to buy a .22, and both the M&P 15-22 and the Rugers were plenty. I went for a used Ruger with a scope and a sling. A fellow at the show I was jawing with said the 10/22 is the Chevy of the firearms world. Cheap to buy, cheap to fix, cheap to accessorize and modify, and like all .22's they are cheap to shoot. He was correct.
Out of the box, the 10/22's have a heavy, notchy trigger (mine did anyway). The same evening I bought my 10/22 I had it completely stripped down, and was stone-grinding the sear/hammer interface (Found a couple of how-to youtube videos for disassembly - you can strip it down to bits and pieces in minutes - same for assembly). A few days later a $10 spring kit I found on Gunbroker arrived in the mail and now the trigger is smooth and light. You can buy trigger kits, extended mag releases, extended heavy bolts, the list goes on forever.
If you're thinking about the price diff, consider you may likely end up accessorizing your 10/22 to the point that it costs nearly as much as the M&P 15-22, if not more. Ideally, it would be good if you could try both guns out before you buy one. My Ruger 10/22 with a 4x scope is very accurate and a pleasure to shoot.