What I liked about Narveson was he was 100% on his extra point tries. Also when he did make kicks they were usually right down the middle. I almost want to say they all were right down the middle but I can't, I don't have that kind of memory. It just felt like to me his makes were really spot on and obviously his misses weren't. I don't have the same memory feel for Carlson's kicks, doesn't mean his were any worse, but Narveson's successful kicks just felt really good to me.
That's the rub with Carlson, if he did have a better % are you just quoting his FG attempts? Because clearly that's not the whole story, he missed multiple extra points. Just looked it up, he missed 6 FGs AND 5 extra points. 11 misses is not a small number. So really not interested in cherry picking only the field goals when that wasn't his only problem. Narveson made 84.8% of ALL his kicks. Carlson made 84.7%. Both deserved what they got.
McManus has never missed more than 3 extra points in a season his entire career. His FG% has fluctuated but as has been pointed out the majority of his misses are from 50+ yards. It sure seems reasonable that choosing him solves the Packers kicking problems for the near future and perhaps for a few seasons to come.