I'm new to the HX Stomp and was curious about this as well. I A/Bed with a tube screamer (not the classic, but the TS9DX from the late 90s) vs the Screamer 808 model, a DS-2 (on both mode 1 and mode 2) vs both the Deez One models, and the Rat (late 90s/early 2000s, but I don't know about the internals) vs. Vermin. I assumed the TS would be the worst model, but found it to be spot on for the TS9 mode and + mode with increased gain on the HX. I never really liked the other modes on the TS9DX so I didn't bother with them. The Rat sounded similar to the Vermin over the distance of the filter knob, but the real one had a slightly fuller, warmer sound. It's passable, but something -- maybe some mid -- is missing. Finally, the DS-2 was "close enough" to the Deez models, but the trashy distortion on the real model was a bit smoother, warmer/fuller and had much more sustain, making it the worst of these models. I figured the DS2 would be the closest due to its more simple and digital aspects and the TS would be the worst, but I was wrong.