I have the Mule 610XC and works well for me. I use it mostly to haul for projects, or while hunting, but if you are going to be traveling longer distances, the 25 mph limit may be a factor. It is a bit slow, but capable, and I am too old to need to go zipping around anyway!
Deciding factors for me were size, price, and reliability. The nice thing about the 610 is it will still fit in bed of pickup when I don't want to mess with trailering. The price was very attractive, and it had good reviews and a good warranty.
Downside in my experience - speed is limited, and the ride is rougher than some others I've driven. Again, around my property these aren't huge factors, but if you are going to be traveling miles of trails, could be a consideration.
The upsides I didn't consider before purchase - comparatively my Mule is quieter than most of the others I've been around. The smaller size means pretty nimble, and I've yet to get stuck or high-centered, even in my pretty rough part of Texas. And the Mule is pretty simple - not a lot of bells and whistles, but fewer things to break - I call it utilitarian!