You might ask the seller about what do they mean by "Demo model", because ther is no such thing as a POD X3L Demo model, but diferent versions of the same serie: POD X3, POD X3 Live, POD X3 Pro.

I agree. Demo =USED. No functional differences.

Because it's used the device may already be registered so you may have a bit of a hurdle when you need to register it to your Line 6 account, but it's a common issue and easily resolved.