I had the XT Live full loaded with all the avaible model packs, and I happily switched to the HD500..

I like the HD500 very much, for several aspects is better than the XTL, specially for the dynamics, the touch and volume response sensibility, and the tweakings options.

If I didn't had need for money I probably would never sold the XTL, but that is also true for several other instruments I sold, I hate to separate myself from my gear.. but space and money are not infinite..

the XTL full loaded with MPs, and also the X3, have some models the HD doesn't have..and many of them are still quite good..

the HD isn't a XT on steroids, they are just different machines, with different characters, both good for different things..

so my personal advice is: if you can, keep your XT Pro and buy the HD Pro, so you'll have all the possible options avaible to you,

PS. I know you asked your question to Pro owners, and I'm not, but the sound quality of the Pro and not-Pro multi-fx above is exactly the same

I had an XT bean...I gave it to my borther shortly after my HD bean arrived...I never had any problem getting a good tone out of the XT. It was the feel of XT that drove me nuts...I could never get a good dynamic feel without adding a tube buffer of some sort to warm things up a bit...The FX in HD destroy the XT...M series FX are way better IMHO...I don't miss my XT bean a bit and both my FBV Shortboards (MK1 greenscreen and MK2 orangescreen) work just fine with the HD bean...

HD: Pros:  1-More acccurate modeling, just by varying your pick attack in the right hand, the possible various tones are many more than the XT. If you spend a day playing the various amps in the HD it will be very hard to go back to the XT models becuase of the finger responsiveness that's virutually non existant in the XT if compared with the HD

              2-Effects sound better than XT

              3-Effects routing is quite open, run multiple drives in a row, or mutliple any effect in any order..Much more possibilites.

HD Cons: 1-EQ is simply terrible, % is used for frequencies and is intended to be "EQ for Dummies" who never a professional EQ in their lives.

                 2-The routing for recording is no where near the flexibility of the XT where you can use POD Farm and route virtual tracks in very useful configerations (hear the wet while you record dry etc tec...

                 3-HD has more bugs when interfacing with a computer that might call for complete resetting of the hardware and in some cases irrcoverable PODs with looping startup screens...

Conclusion: POD HD modeling is superior in every way so I can never go back to play with XT level modeling, it just sounds like a toy in comparison and I'm willing to go to hell and back to have that quality tone. To me everything else is irrelevant when it comes to tone, I already have recording setup and I'm not counting on the POD having any recording (ASIO,) drivers. Actaully I wish they take many of the features for recording out and focus on the quality of the models. The New Soldanos in the HD are leaps and bounds ahead of the XT...