You can make more money on commission, but the problem is (Imo) is that it puts stress on you to hit your sales goal, which puts you at a risk of termination do to not hitting your sales quota. That means you are going to try and sell everything under the sun, vs what the client needs.
I get paid hourly and judge on calls backs. My bosses are cool, they don't care how long it takes you, and don't make you rush call to call, or rush the job, proof, company policy states if you get a speeding ticket in their truck your done, pack it up and go home.
When we run in to issues and it needs to be fixed right then and there, all they ask you how long will it take you, and you tell them, they call the client and give them the quote, which takes a lot off of me. Quotes, and customers authorization is all them, so if there is an issue, they deal with it, not me

. My bosses take a lot off of us, and are the easiest people to work for.
All they want us to do is quality work, not quantity.
Call backs cost you money, and makes the company look bad.