>>13229516Austin's best work was the Austin v McMahon feud. This isn't even in dispute. It is continually, and rightfully, credited with turning the tide of the Monday Night War to the WWF side. Austin was the hottest during this feud, with Vince giving us some of the best heel work ever too. Both were firing on all cylinders.
Austin's best match (and the GOAT) was vs Bret at WrestleMania 13, but that one doesn't have anywhere near as strong a feud behind it. It becomes the basis to the Hart Foundation storyline, but predates it, and occurs after Bret/Austin at SvS, which was supposed to be the end of their feud. Bret was supposed to wrestle Shawn for the WWF title, but that changed when Shawn refused to lose to Bret. So the Austin/Bret match wasn't a continuation of their feud from SvS.
The period of Austin's career where he had the highest work rate consistently, was as Stunning Steve in WCW.
So it depends what you meant by "best work" but storyline wise and drawing power and public perception, that was during the Vince/Austin feud.