For a while I put a 34SC 120 on my Vertex, and I really liked it. I didn't find the geometry differences very noticeable and it was nice to have a stiffer fork with more travel. The only reason I didn't leave it like that was that I needed that fork on a different bike.
This paragraph is more about comparing the forks than specifically about the forks on the Vertex: In my opinion its just a trade off either way - the 34SC is slightly heavier (about 1/2 pound) and slightly stiffer laterally (at least compared to a current 32SC - comparing to my older 2017 32SC that came on my Vertex, the 34SC is way stiffer laterally, but that was before they added a little more weight to the 32SC crown to make it track better). I'm currently running a 32SC on my 2021 Element (70 XCO build), and I thought I would want to swap out the fork to the 34SC, but I am finding that I really love the way that bike feels with the 32SC - so light and fast on the climbs, but still just enough suspension for most any trail where local races are held. I wanted to order an Element in the Carbon 90 build, but only the Carbon 70 XCO was available in my size so I figured I could just add a dropper and swap out the fork and lower headset cup. I did add the dropper, but I'm actually going to leave the 32SC on because I love the way the bike feels for XC racing like that, and as I said, the 2021 32SC is noticeably stiffer laterally than the older version (I think they changed it in 2019 or 2020 models?). However, if I was more focused on riding the bike for fun or longer endurance events, I would switch to the 34SC, which is still overall a much more capable fork at high speeds when things get a little chunky. (And with Fit4 Damper is actually only maybe 100 grams or so heavier than the Performance 32SC with the Grip damper that came on my Element, but I am planning to swap to the Fit4 Damper, as well as upgrade the brakes and cassette to XTR to save additional weight).
