Hello,
thank you for the new info.

I'm pretty sure that a new XBox One here can't be find with a price lower then 250€, probably our marketplace have differences on this side.
I red there was some non-free PS2 emulator on the One (Indiegogo and XPS2E) and I assumed that it could be emulate any other system (including Saturn and PSP of course)

Also, the information I found originally was different: I red that Xbox One could run 33 games of the original XBox readapted, while Xbox 360 was totally retrocompatible with the first console, so I expected it could run them exactly like the original Xbox.

In this case, if running Panzer Dragoon Orta on X360 is painful and the console is not able to emulate other consoles properly (and I'm thinking particularly to Saturn and PSP), also this option won't be good for me and I'll get back to PC option.

I did the right thing asking here, as I could buy one of the consoles to find myself not satisfied with it.
I'll wait the day I can play Panzer Dragoon Orta on a PC some way.

Thank you!