First of all: Everything is a matter of taste, you might have different expectations than I do.
I had a chance to listen to the 3 Yamahas DXR10, DXR12, DXR15 in a well equiped showroom. All 3 were in head high position, roughly 1.5m (5ft) off a sound treated wall.
First I just listened to all of them using some music, pretty loud but not even close to max. First I didn't care about the currently set mode on the DXRs. The DXR10 immediately sounded better than the DXR12, there was no "life" in the DXR12. The DXR15 was amazingly good in my opinion, because I expected it to have just to much lower end. But that didn't happen.
Then I checked the mode they were set to ... and I should have known before, the DXR10 was set to FOH/MAIN while the DXR12 and the DXR15 were set to OFF.
Next I switched all to FOH/MAIN ... and what happened then was: I still liked the DXR10 best, the DXR12 got more "life" but there was something missing in the mids ... and the DXR15? Man, the DXR15 really started to move considerable air. I didn't notice any problems in highs or mids, but the lower end was amazing and a little to much for my taste at the same time. It didn't loose definition in the mids and highs but wow, the bottom end department clearly exploded. If you like really fat tone, this one should be a safe bet ... although this beast is huge and heavy. But if you prefer clearer, crisper and balanced sound with still enough bottom end, then the DXR10 turns out to be the best option, in my opinion.
I was surprised that somehow the DXR12 turned out to be the bad boy in the family ... well, not really bad but a noticable hole in the mids that I didn't like.
Hope this helps, although it's highly subjective.