I had considered the MTX bag/pannier setup, but what I've found is that I vary my load depending on the season, and 70% of the time only have a pannier on one side. If I had the MTX system, I'd have empty bags most of the time, so have stuck with my separate pannier format.
The mounting system on the MTX is pretty cool, but in my playing around with it (when considering a purchase) it seemed a bit flimsier and sat higher overall than dedicated panniers.

Most panniers have a quick-latch type system that allows easy installation and removal.

Topeak racks are good. Of their line, I have used and really liked the Super Tourist with the lower side rails.