As far as I'm aware, from the discussion above, it seems like Ben gets out-haxed here rather badly, as Henry has a myriad of ways to get rid of Ben, whereas Ben's only true win condition is existence erasure via Alien X. However, even that comes with some caveats. I've watched Ben 10 Classic, AF, UA, OV and even some of the reboot, and Ben using Alien X to instantly erase people has never happened. Hell, Ben going instantly into Alien X is something that we've never actually seen apart from him versus the Rooters. And against the Rooters he simply wiped their minds instead of erasing them from existence. Henry should win here, methinks. It'd be super OOC for Ben to wipe someone from reality.
Edit: Forgot to mention but Henry could also potentially just come back from EE, as he was able to retry after having his universe 'erased'. The only reason Alien X even has existence erasure is because Servantis said that he could 'wipe everything from existence', which could just as easily be as much of an AP feat as Henry coming back from universe erasure, so I think it should count.