I helped Think Tank Photo launch the Roller Derby back in 2013 and it is still my go-to roller! The four wheels make it so easy to let the bag "heel" (like walking a dog) alongside you instead of pulling a two-wheel bag. It's slightly smaller than the Airport International but I used it comfortably even before I was using micro-four-thirds system.
Careful on inclines, the wheels don't have brakes! Shop on Think Tank Photo
Shop on Amazon