The Otis is good at cleaning and it's safe. I use it for my M1, where the breech is inaccessible for a one-piece rod.
The one-piece rod is faster and easier. That's what I use for the AR. If you want to clean the AR without field stripping it, the Otis will work. But what does that save, ten seconds?
For walking in the field, the Otis is easy to throw in a pack or hang on a belt.
Either way, that's just for cleaning the bore. You still need brushes and solvents and rags for the rest of the bits. The AR generates a lot of black mess, with that gas system. Spray cans of brake cleaner help a lot.
Regards.