when I mess a diaper, which is seldom, I am always alone and have a good place to clean up. Remember, the smell will invade the whole house in most cases, don't think you can do this with others in the house that you don't want to know. I prefer clothe diapers, but wear disposables. I find bigger diapers can be tapped up snuggly. Smaller is not preferred by me. I also wear plastic pants. This is a turn on for me, but also practical when wetting or messing, it provides extra leak protection. Also, when you are going to mess a diaper, it is better when you feel the mess is going to be more solid, than say, something like diarrhea. Large and hard movements are better contained, create a better fell in the diaper, and reduce the risk of leakage. Store brand diapers will do, but you'll always get better diapers from hospital supply stores. That is a common experience of most us DL's or AB's.
As a kid, I messed myself mostly. It wasn't till I was an adult that I learned the joy of wetting myself. Both are great sensations, but wetting is preferred simply because of easier clean up. You can wet yourself without others in the house knowing. All in all, I prefer messing a diaper, but mostly wet for convenience sake.
Good luck, experiment and see what your like are.