Top speed is determined by more things than just HP. Differential gearing and clutch set up are two big factors.

I had a Polaris 850 Touring that I hit 78 mph on the highway one time and that was enough for me.

My BF tops out around 63-64 mph but would eat that 850 easily from zero to 30-40 mph

I prefer the power to be on the bottom end rather than on the top end where I rarely ever go.

My average speed for nearly 9000 miles is in my signature.

Want to go fast?? Buy a sport quad.

 

The Polaris is an inline twin vs the v-twin for the Kawasaki. In general, a v-twin is quicker on the low end with comparable displacement while the inline twin has more top end speed. I agree though, low end power is more important for an atv. Most of the time you're not running even close to full speed unless you're on pavement. You need the low end power to climb hills, get through mud, pull trailers etc. And in general trail riding considering most of the time you're usually not going that fast. Most single cylinder machines have good low end but fall off on top end. 0-30 mph is plenty quick for the bigger singles I've owned, being the King Quad now and Grizzly 660 in the past.

 

I would definitely agree the low end torque is better, I would say my average speed probably matches Specta's pretty closely. Our trails are just to narrow, steep, and have a lot of drainage dips to even think about building up any head of steam, Plus you miss everything when you ride to fast

 

I like my pace to be somewhere in the middle. I don't like poking around but not flying around so fast that I lose control. There's a happy medium that makes it relatively safe but still fast enough to be fun and exciting.

 

Gearing can be a huge factor. But when comparing 2 V-twins, or 2 singles, etc., the bigger engine is usually more powerful. And the more powerful ATVs are usually faster if the gearing, clutching, and weight are even close to being the same.

My 500 isn't very impressive, but I didn't buy it to impress anyone. It's quick enough for me from 0-30. Anything above that doesn't matter on trails where I average 15 MPH, or 20 if I feel the need for "speed". I can ride down the road doing 45 MPH at about half throttle, or give it full throttle and get up to about 55 and burn more gas. My friends going faster will wait for me to catch up when we get to a trail again. Even if I could go faster I wouldn't want to.

 

There are times I'm pushing mine past the limits of my abilities. Then there are times I'm just creeping along in low.
I'm averaging nearly 2 mph faster than I did on my Rubicon.
I'v ridden lots of atvs over the years and the Brute Force has the best low speed throttle response out of them all.
The 850 Touring I had for a while definitely had more power but its delivery was not the same as the BF.

 

I liked the Brute Force a lot. I just wish they made a 2-up machine. I found it compared pretty closely to the Outlander 650 in power delivery.

I don't like how Polaris' clutching engages either. It's way up on the RPM range and feels like you're waiting forever to get it to engage. I really like the Can-Am clutching a lot. Comes on very quickly and modulates easily too. You can either punch it and scream off into the distance or it's very controllable to roll into the throttle smoothly. Especially with the 1000, I find the control to be fantastic.

 

I think on the Polaris its the way the belt engages. It has to build up rpms before it will engage and take off. It allows the belt to slip before it kicks in. On Yamaha for instance, you have constant belt tension so it engages the instant you hit the throttle. Polaris belts must be pretty beefy to be able to last.