I would have to come down on the side of the 1911. The 1911 is exceedingly easy to work on and I've found mine to have accuacy that is excellent. BTW, mine is the Ruger SR1911 of which I now have two. As for why two, it's simple, one will get the Ed Brown Bobtail mainspring housing and grip modification.

As for the accuracy of my Rugers, they are too close to call a difference. One thing I really appreciate is the sights, they are easy to see for even this old fart who normally can't focus on handgun sights anymore. I've shot both Rugers to 1.5 inces at 50 feet so I'm quite happy with their accuracy. About the only real negative with my Rugers are the magazines, they are not nearly as smooth to load as Wilson Combat magazines so I've stocked up on Wilson 47-D's and benched the Ruger Magazines. BTW, the Rugers are Combat Sighted with 230 grain bullets, something that I prefer. When focusing on the sights is difficult having the dot in the front sight correspond to the POI makes it easy to score well. In addition since my Sigs and revolvers are Combat sighted it means I don't have to adjust my sight picture for the Rugers.

Muzzle flip. Really, are we going to bring that up. First, the 4.5 inch M&P weighs in at about 30 ounces and a steel 1911 will run 38-39 ounces. That lighter weight will pretty much negate the advantage of the slightly lower bore axis on the M&P. In addition I think that muzzle flip is way way oversold on both the internet and in gun rags. The plain and simple truth is that only about 1 to 2 percent of handgun shooters come even close to a firing rate where muzzle flip will impact their split times for accurate fire. BTW, I have a CED 7000 that I train with so I know my split times, how many others here use a shot timer?