For 2015 Polaris smacks an all-new Polaris ProStar 1000 engine providing an industry leading 107-horsepower and a 999cc displacement into the RZR XP series...

First Look: 2015 Polaris RZR XP 1000s | ATVConnection.com

 

Still my favorite of the sxs sport models.

I'd go with the 2 seater.

 

that is a bad-*** looking ride!
atv mag should do a comparison of the sxs vs. atv rollover apex.

the major component keeping me off those sxs's is the fear of rolling it. for example;
with the atv, you get to manipulate your machine with "body language" and the throttle...
with those sxs's, all you have is throttle, basically you just sit there and hope for the best.
one of my favorite things to do on my outty 1000 is floating around corners on dirt roads, kicking the back end out just by simply shifting my weight- can't do that on a sxs...

still- a bad *** looking sxs!

 

For the 50" side by sides I think your concerns are valid. Also consider the fact that on an ATV, if you're on a very narrow shelf trail on the side of a mountain, and the ATV starts to go over the side, you can bail off, and at least save your life, even if you cannot save the ATV. With a 50" side by side you are usually seat belted in, or there is a side netting that is preventing you from getting out. And if you're on the downhill side, you couldn't get out anyway. Sometimes the bottom of the mountain is hundreds of feet down, and they don't build these roll cages strong enough to survive that kind of rollover. So on the super extreme terrain, an ATV is safer. But in the side by sides favor, the seating position in the side by side is usually much lower than on the ATV, so center of gravity is actually better than on an ATV. In particular, the 64" wide sport side by sides feel very stable, and are natural power sliders in turns. For normal side hills, uphills, downhills, that don't have the risk of a long long long roll to the bottom, a sport side by side like the Rzr 1000 in the picture above feels much more stable and confidence inspiring than any ATV does.

 

Center of gravity may be better on flat ground but there is no way to shift your weight from one side to the other around turns or on a incline. For a beginner , sure the utv will inspire more confidence on some simple climbs and corners but once you learn to utilize your entire body, the atv has more potential just about everywhere. smaller, lighter and faster. Also the weight is centered on a atv where a utv with one passenger will have a driver side weight bias.
Baja 1000 is a good measure to use because everyone runs the same course with a mix of just about every type of terrain. The atvs finish in nearly half the time of the utvs. Just takes a better rider to get the most out of a saddle machine

 

I disagree that the center of gravity is better on a sxs than on an atv.

sure- YOU may be seated a bit lower (not much lower) on a sxs than on an atv- but the engine on an atv is under the rider- not behind him like on a sxs. And, what little gain the sxs may have on the atv is totally lost by the fact that there's a roll-bar and a ton of other gear positioned ABOVE the sxs riders head (well above atv seat height) and this "extra" higher weight (that atv's don't have) would negate any real benefit a sxs might have from a lower rider position.

as far as power-sliding around corners; I can slide my outlander around a corner just by simply shifting my weight- can't do that on a sxs.
and... lets see how long you can hold your breath after rolling your sxs under water. If I roll my atv in deep water- all I have to do is... stand up.

 

No offense Beergut, but I would like to know how much time have you spent driving a pure sport side by side? I've owned a few of them (2012 Rzr XP 900, 2013 Wildcat 1000, 2014 Rzr XP 1000), and have thousands of miles on them. I've also owed a 2012 Outlander 1000 XT, and have logged a lot of miles on it. The Outlander doesn't have a whole lot of bragging room when it comes to sidehill stability, and that particular ATV is way more tippy than a pure sport side by side. Yes, you can shift your weight on the Outlander, but then again, you have to shift your weight. Keep in mind I'm not talking about the utility side by sides like the Rhino, Big Red, Teryx, and especially not talking about the 50" wide side by sides.

I'm not worried about standing up in deep water, because I live in a desert. But as an example of what I'm talking about, with my Wildcat 1000, which is the most stable of the side by sides, I remember trying to see if I could get it to feel tippy. We were at a large sand dune area (Little Sahara, UT) where they have big dunes that can be over a hundred feet high (the tallest dune is 700 feet high). The steep side of the dunes are as steep as you can stack sand, and I was having some fun with the Wildcat, seeing how well it could sidehill. I ended up being able to drive completely sideways on the steep side of the dune, and stopping like that, and having the side by side slide sideways down the dune. But it never did get to the point where it felt tippy, or have problems lifting the uphill tires. Try that with an Outlander 1000, and you would have to stand completely on the uphill sideboard, and it would still be spooky with that ATV sliding sideways down the dune.

The pure sport side by sides are stable, and don't feel tippy. They have up to 18" of suspension travel, and can crawl over uneven terrain like a big spider. And that helps them keep all four tires on the ground a whole lot better than an ATV. They're better than an ATV for stability in a lot of areas. But there are also a lot of areas where ATVs are better, at other things.

 

Engines on the RZR 570 and 800 are about the same height as the ATVs. The rider increases the center of gravity more on a quad. The actual frame of a RZR is lower than the quads too.

I guess flipping over is a concern when you're someone that looks at a quad and it flips over...

 

Used to be a group of guys down around the Houston area that posted videos here of them running mostly the rzr, but a few other sxs's too.

Found this one. It may require a little extra gear if you want to try this at home.

 

Just made my short list