I own:
5153 100w Stealth
5153 100w EL34
5153 50w 6L6
Peavey 5150
I’ve played but don’t own:
5153 50w EL34
5153 50w Stealth
5150 Iconic 6L6
Peavey 5150 II
I have two answers.
If you can only have one amp, no post processing, no boosts, just an amp for playing in a band setting, I’d pick the 5150 III 100w Stealth.
If you have all the pre and post EQ tools you want so you can shape both the character of the distortion and the overall EQ signature however you like, I’d pick the OG Peavey 5150.
The 5150 III 100w Stealth sounds like an OG 5150 but more modern with an internally hardwired low cut before gain for some extra tightness and in my opinion a much better tonestack than the OG. However, the less filtered nature of the OG 5150’s preamp means it has a guttural kind of low end thump and a fullness or richness I don’t really hear in any of the other amps in the series and prefer over the other versions. However, if you use your own pre-EQ, you can blend anywhere between that low end thump and the tighter, more “modern” sounding 5150’s with built in low cuts. As for the extra post-EQ either in the loop or actually in post, I just think the OG’s tonestack isn’t as good as the 5150 III tonestack, but the OG’s preamp is good enough that i think it’s worth messing with another extra EQ in the loop to compensate.