You're asking the kind of question that makes me sigh a little, because chasing 'best quality' with MTL is like looking for the cleanest puddle after a rainstorm. MTL, by its very nature, is a compromise. You're not going to find a site that consistently turns out polished, readable prose from raw machine output, because that would require human editors, and then it wouldn't be pure MTL anymore, would it? The places that host this stuff are often aggregators scraping from multiple sources, and quality swings wildly not just from site to site but from chapter to chapter within the same novel.
That said, I've stumbled across some aggregators where the underlying raw translation seems slightly less garbled, maybe because they're using a slightly better engine or the source text is cleaner. I've noticed some web novel chapters on sites like Wuxiaworld's forums or NovelUpdates listings from 'unknown' translators sometimes have a MTL base that's been lightly touched—maybe someone ran it through Grammarly or did a single proofreading pass. It's still messy, but the character names stay consistent and you can mostly follow the plot. It's a far cry from a proper translation, but if you're desperate to know what happens next in a story that's otherwise stalled, it gets the job done.
Honestly, after trying a few, I've come to treat MTL as a last resort for unreleased chapters, never as a primary reading source. The mental strain of deciphering awkward sentences often outweighs the satisfaction of advancing the plot. If you must go down that path, your experience will depend entirely on the specific novel and which aggregator scraped it most recently. I'd just search for the novel title directly and open a few of the top results to compare the first chapter; you'll see the 'best' one for that story pretty quickly, but it likely won't hold true for another title on the same site.