I owned few RAT based pedals: BSRI Audio SFG, Earthbound Audio Iron Pig and Deathmaster.
Of all these I've kept only the SFG, because it sounds more modern than a normal RAT would (it has a 2 band shelving EQ and a super cool clean blend you may also use as a clean booster).
Iron Pig was also cool, many options and tweaks available, very vintage to my ears (when compared with the SFG).
But the RATs have such a peculiar way to distort that I don't personally like so much.
I find them to be super nice at low gain, but when you crank up the gain to me it sounds to rough and "sputtery". I better like HM2 or Big Muff, which tend to be more versatile and fluid.