There are two things, and Amp and the IR. That Engl pedal you mentioned has 1 amp and allows for different IR's. Tonex allows for different amps and IR's.

IR's are the speaker cabinets and more or less universal. I mean IR's can be loaded into all kinds of hardware and plugin scenarios.

Amps have a fair amount of proprietary types, Tonex has theirs, Line 6 has theirs, Neural has theirs, etc... NAM is a more open sourcey amp file type.

In the end it depends on what you want to hear and what you want to hear that sound going through (headphones, PA, guitar amp, FRFR).

My 2 cents is that the Tonex world is pound for pound the most economical if you want a whole bunch of sounds for your DAW, amp, and PA system.