Alright! A rather interesting match, that I'm kind of jealous I didn't think of first. Now then, let's check their stats to see who comes out on top.
Since speed is equalized, we'll move on to strength and durability. In terms of strength, I'm going to have to give it to Jenny, mostly because Mettaton has never shown any real strength feats. And as for durability, I'm also going to have to give it to Jenny for her Invulnerable Titaniun Alloy shell, because even though Mettaton is a very durable enemy, one of his attacks does leave his heart-shaped core exposed, which could be turned against him in a heartbeat. (Also, Jenny doesn't have a SOUL, so Mettaton's attacks can't hurt her this way.) Jenny also has more combat experience than Mettaton does, and she's actually more intelligent, considering her vast array of knowledge provided by her mother, as opposed to the very limited base of knowledge Mettaton has. (His overall vanity doesn't help here either.)
Ignoring the fact that they're both robots, so neither of them can really wear out, a lot of Jenny's weapons can actually deal with Mettaton's bot and bomb Creation, and her Flight gives her a fantastic aerial advantage over MTT. And while Mettaton has been shown hacking into the door to his room to seal off Alphys from getting in, Jenny is a very complex robot built by another robotic genius who has a completely different design than that of himself or the CORE, so it's highly unlikely he'll be able to hack into Jenny and mess with her.
Probably the biggest problems Jenny is going to face from Mettaton is his laser disco ball, and his overall Danmaku. However, Jenny has fought plenty of characters who attempt to overwhelm her with firepower, so she's more than capable of handling that, and while the disco ball may prove a problem for her, this is only one attack out of many that Mettaton is likely to do, and honestly, it's not very exciting to just spam the same attack over and over again, since he is a performer and all.
Overall, Mettaton is just simply outmatched in every way, shape and form in this fight. That doesn't make it an outright stomp, as Jenny will have some trouble putting this superstar down. But, in the end, it seems that XJ-9 will be able to put down MTT with flair.
Winner: Jenny Wakema
