v22 mags

Interesting question, because I'm guessing the answers will vary. I, too, assumed the metal ones would work better, but I actually prefer the function of the plastic ones. I could be wrong, but they just seem to cycle more consistently in my rifle. On the other hand, the plastic mags are 10 rounds and some prefer the 12 and 15 round metal mags. So, no definitive answer?
 
The plastic ones are easier to load. The aluminum ones due to the length of the spring to load the 13-16 rounds can cause rim lock if not paying attention when loading.

I am careful so I don't have problems with either. But I have friends who have lazy loading habits and can get mag feeding issues.

I run 10 poly 10+1 poly and my 12 (fits 13) aluminum mag. I also have a 15 (fits 16) mag I run for the high round count stages (only have done 2 in the past year).