We haul a lot of larger excavators for contractors and dealers all over Indiana. Just moved a Cat 385 last week, big sumbitch!!
With the newer machines, I'd give the edge to Komatsu. Their hydraulics are just silky smooth, especially the PC600's. Nice all around machines. But really with most of the current excavators, you're really splitting hairs to say one is much better than the others. All of 'em are really nice machines.
With that said, the only one I own now is a Hitachi EX300. At the time I bought it, I was really impressed with the swing speed. You could load a trial axle in 7 passes with a 20 second cycle time. I do think that the Hitachi hoes have suffered a bit since Deere took over the US distribution (and I like Deere equipment). They just seem slioghtly lazier than they used to.
You can't find used hitachi equipment. That tells me one thing. Your right they are faster but that's cause they are geared higher. Put a hitachi and komatsu on a slope and the komatsu will swing a heavier load. This is with the older machines (90s models, EXs and what not).