I got the Elecom Huge a few months ago after seeing this thread and it's been really nice. I do think the mouse is objectively better when it comes to precision, but outside of gaming I'd wager most people don't need one unless they're doing graphic design/3d modeling/etc. It's less strain and more fun to use a trackball IMO, as the main motion is spinning the ball in the right general direction, then making corrections as it nears its target.
Some notes: The bearings in the Huge do wear down after a while and become tolerable, although I only found this out because the replacement bearings I ordered from a "US seller" ended up being some kind of Chinese operation that just took my money and ran (I got a refund eventually.)
I will say the name is misleading since it's designed for Asians, who I guess have smaller hands since my average-sized hand still misses the "hump" of the wrist rest by a bit. Regardless, it's a wrist REST, so your hand should only be on it when you're idle anyway - at least that's what I'm told. I float my hand over the trackball when in use, and I normally use two fingers.
The scroll wheel is fine, but inferior to binding a button to emulate middle-mouse scrolling via the ball. That way you can hold a button and just fucking torque the thing and go flying down pages. I bound it to the forward-most button on the side, which feels better than using one of the top buttons on the right.
I did pick up a Kensington Expert today and am surprised by the lack of resistance when moving the ball. It's a feather compared to the Elecom, which is good for per-pixel movements, but kind of a pain for more general movements. I'm still tweaking it quite a bit since the ergonomics are completely different. The scroll ring is a neat idea, but overengineered as shit. I took it apart and removed a magnet they'd put in there to keep it aligned with the sensor used to detect scrolling, but it still feels a bit stilted. Might have to lube it up somehow.
I'm curious to try one of the CST trackballs next since they're held in such high regard, but the used market is through the roof after the maker retired. Apparently they were bought out and are restarting production in Q1 2020, though.
Thanks for making the thread, OP. Really been fun learning about this stuff.