So I have got the POD HD500x and used it in the studio. Definitely not as good sounding and as good dynamics as the AFX. I had the master volume completely cranked (max) and it still wasn't very loud into the Rivera. I used the same setup (into efx return of rivera) and it was very loud on most presets with AFX on 2/10.
So I still enjoy playing with the HD500x at home with garageband for practicing/recording but it's not as pro a unit as the AFXII obviously unless I'm doing something wrong which I doubt.
I do like the fact that it has a CD/MP3 in jack but it doesn't even have a power on/off switch! wow. Reverse scenario for the AFXII.
The editing software for Mac is hard to read and I couldn't make it larger on the screen. Also, the LCD screen is hard to read as well. However, I liked the fact that the drive/treble/bass/mids knobs were real knobs, not virtual, makes it easier to adjust.
I still think that the HD500x is a good value for the money but I'd be surprised to see any pros using it. I only found a couple of dirty presets I liked but more cleans and effected that I liked. It's convenient that it comes with the floorboard/footswitches. Will AFXIII come with floorboard and MIC? thx.