The wide body format has its advantages as outlined above. However, I usually advise against it because of the aisle issue you mention. My normal roller is 22x14x9. There are already moments EVERY TIME I roll it down the aisle where it catches a seat or bumps into a leg that's placed slightly into the aisle. The fact that due to the position of handle and body it is not exactly centered in the aisle has to do with that, too.
If you are always in the front rows, no problem. But if you have to carry a 30lb case to row 30 in a packed plane, not funny.
I'd go with a 20x14x8 inch bag. Even my full-size bag fits wheels first in all cases except those where it wouldn't fit even sideways and has to be gate-checked. So the slightly smaller size should give you the decisive edge especially with sizers and smaller bins.
Till