A lot of companies are trying to get into the SxS or UTV market because they've seen the successes that Kawasaki, Polaris, Yamaha (to an extent), Honda and CanAm have enjoyed for a good while.
You don't hear much about the gravely brand, just like the Cub Cadet brand, Intimidator brand and many others. And for good reason. Note that they all have pluses and minuses, and really the only way they sell any of them is on price. They're cheaper than the more well-known brands, and they're also less expensive
I sold Kawasaki, Yamaha, and for a little while Intimidator. Oh and Kubota. Did Kubota for almost 30 years, we did intimidator from 08 through 2015. Intimidator was a spinoff of bad boy mowers originally so the "technology" largely came from their lawn mower lineup originally. The lead engineer who was in charge of the bad boy mtv vehicles originally was a good friend of the owner of a well-known Polaris dealer in town, so they copied Polaris on a lot of stuff, but used lawn mower "tech" elsewhere. Then Bad Boy ditched one of their owners, who started his own company called intimidator. Initially they took a lawn mower engine (kohler) and mounted it to their own chassis, which was based on Polaris but with lots of changes made. The belt drive was a dirt cheap setup, with NO COVERS, so any splash would cause belt slippage. I mean, what were they thinking? So you get the idea. Yamaha owned the SxS market locally for 5 or 6 years until the whole "Rhino lawsuit" deal--where some people went after Yamaha for building a "unsafe" side-by-side. It in itself was not unsafe, it was perfectly safe but the owners were doing stupid stuff with em and getting themselves hurt. Kawasaki didn't have anything to compete so they COPIED the Rhino in 2007/8 with the Teryx 750 which was a Brute Force 750 engine mounted on a copied Rhino chassis. That thing was junk. But, they sold tons of them (and ate the engines on tons of them) which told them, hey, there's a market for this. 2012, it was redesigned for the better, still a 750 but a lot better. 2014 it became an 800 and it's been 800 ever since. Oudated now but that's also why they've decided to build the teryx 1000 (KRX1000) and Monday I think, they're unveling the "ridge" which I know nothing of. I think it's gonna be a competitor to the Polaris Xpedition.
Stick with a Mule if you want 100% utility. If you are VERY patient you can probably use a Mule SX but I guarantee you that at some point you'll wish it had more power. 13hp is barely enough. It is inadequate for any trail riding and/or real work, unless your trails are totally flat and manicured such that the 3" of suspension travel won't beat you up too much.
Kubota also has a line of utility vehicles, but most of them are centered around a diesel engine and a hydrostatic transmission. Exception is the sidekick which is a version of the "standard" CVT (belt drive). It is a cheap version of a CVT. I can't speak for the newest sidekicks but the 2020 and earlier models had a horridly over-reactive throttle, which made them mostly uncontrollable on rougher terrain. You couldn't pay me enough to ride on one the trails here. Polaris uses electronic throttle which I initially hated but the first time you are on a rougher trail you'll appreciate it. Polaris has them set up such that bouncing around doesn't automatically cause jerky throttle operation. Rzr line is a lot more sensitive but still NOTHING like the sidekick. I don't even consider a sidekick when people ask me "which brand". I'll suggest a Gator before a sidekick. The hydrostatic transmissions eat up too much of the engine's power on the diesels. Those engines are real powerful but you'd never know it because of the transmission. HST transmission in this application just does that. If you mash down on the go pedal while in a rut, and the wheels won't spin, they're not going to spin-and depending on the temp of the transmission, may very well kill the engine. They can take up to 25hp to run the transmission and the engines don't make any more than that. I do not like the HST design for this purpose. Stick with a CVT or go to a fully manual 5 or 6 speed straight gear transmission. But they can't do that because 96% of the target market can't drive a manual transmission. It's nuts.
Polaris' new ranger 1500 is impressive for a work horse. Real torquey, really smooth, rides excellent. I've been impressed with them.