Yeah, I dig the DT25 XLR output! I play rhy guitar in a two guitar four piece, and we still struggle with mic'ing the lead guitarists amp (40w Fender tweed). I have tried a few different mics and mic placement; my DT25 signal just cuts through the mix with zero effort - and zero 'bleed' from the band.
It's a sweet sounding signal, I dig it. I like it way better than going direct from the HD500 into the mixer. I even tried going XLR from HD500 to the main mix, and using a 1/4" from the HD500 to the FX return of the DT25.
For me, the key, is the Bogner contribution. For the most part, all the amp modeling from all the different companies is more or less comparable. I just can't afford Axe FX, and I tend to not like Boss for no really good reasons - but in a blind test, all things being equal, I would be hard pressed to tell the difference.
Amp modeling has come along way, Line6 remains at the forefront, yada yada, etc.
The key to the HD500 - DT interaction, is that it goes BEYOND amp modeling.
While the AxeFX is awesome, it cannot tell the Bogner analog poweramp to switch relays and change it's ANALOG components to 'become' the amp being modeled. And that's what you get when you use the DT25/50 XLR out. You get an interaction between digital preamp and analog poweramp, that cannot be compared to any 'pure' amp modeling hardware or software.