I'm not talking about clean tones, lol. I'm talking the quality of the distortion. I've owned 3 Soldanos, including an SLO. The SLO needs to be cranked to ridiculous levels for those power tubes to get workin'. I gigged one for many years, and know the sound well. Master at 6 was just too much, but that's where the power tubes finally filled in the sound. It's still a more compressed sound than an old plexi or even a single ch. JCM 800. Unless you used the crunch channel, and that's what I liked best, because it didn't fizz out as much.
I just like his old Marshall tone more, as do most folks. Nothing to do with vintage. Just a killer, sound, and is unique because it was so dependent on him and his playing to get that sound, not a lot of preamp compression and gain. Listen how clean his live tone was. Single notes sounded very "clean" with not too gainy or fizzy like in the (video right above), but they had sustain.
He probably would've taken a Wolfgang/5150 back then and I'm so glad they weren't around then. He had to work hard for the sound and that's how he got that great tone, by playing the **** out of the guitar and amp. He's said in many interviews that he didn't want to work hard for that sound.