There’s a thoroughly comprehensive review here that’s worth reading:
Personally I think the Pro is a solid, if expensive, upgrade—and it’ll be even more expensive if you need to buy the Fleshlight adapter too. I don’t know if the plain Handy 2 is as much of an upgrade if you already have a Handy 1.
The extra travel I haven’t really noticed over the H1, but once I overclocked the H2P it has been much more impressive and it’s much better engineered so is quieter and more sturdy. I’m sure it’ll handle heavier sleeves better than the H1. I don’t like the button placement on the side though, think that’s a bit of a step backwards.
The threaded screw mounts on mine are solid, but then I just use an Arca Swiss style quick release plate that’s permanently attached and would strongly recommend everyone does that—you screw the quick-release plate in once and then it’s much more robust to quickly attach/remove. Something like this cheap plate + mount + ball head works very well: