A harder push (from a larger fuel / air explosion) on a lever (connecting rod) will apply more torque to a rotating mass (the crankshaft), assuming the levers are the same length. Another comparison would be to put a lug wrench on a lug nut then have a person step on the lug wrench to apply force to loosen the nut. What would apply more force to the nut, having a 100 pound person stepping on the wrench or a 200 pound person stepping on the wrench?

If both cylinders of a Polaris 700 twin fire at the same time then the force would be equivalent to a single cylinder 700 when it fires. I have heard that the pistons of a Polaris twin go to TDC at the same time but I would have thought (from the sound the engines make) that one is firing while the other is on the exhaust cycle.

A Polaris machine does have an advantage over the competition when it comes to towing simply because of it's weight. Beyond towing (except maybe under certain compromised traction conditions) I don't think the weight would be an advantage.

The power steering unit is progressive (applies more torque to the steering stem the slower you go) but my trail ride speeds vary from about 8 mph (narrow, rocky trails) to 40 plus (more open woods trails), averaging probably in the mid to upper 20s where I typically ride. I can state from experience (as can others that have ridden my 700) that the power steering unit substantially reduces bump steer and the resulting shock to the bars than what you experience on the non EPS equipped 660 Grizzly for instance making the 700 Grizzly a much more stable trail rider. Riding the Grizzly 700 makes it easy to drive with one hand while using a machete with the other when we do trail maintenance on the farm.

I personally prefer complete manual control of things like 2WD, 4WD, 4WD lock and braking (independent front and rear brake control) when it comes to an off-road machine like an ATV. When riding on a technical trail that I'm not familiar with I'll just punch the 4WD button so I'll be ready for the unexpected since you really can't tell the difference in steering on the 700 Grizzly (between 2WD and 4WD). Having it in 4WD just makes it a little harder to slide around corners when the opportunity presents itself. Now in an automobile on the road (where speeds are typically much faster) I prefer anti-lock brakes and automatic traction control / AWD.

Even if you weren't in 4WD pushing the button with your thumb is effortless and you can do it while you are moving. However you must stop first if you want to engage the diff-lock. This has not been a problem for me anyway because when I'm typically in a situation where I feel I need to use the diff lock, I want to stop and look it over first anyway rather than just dive headlong into it without any sort of evaluation or planning.

As for top speed the 660 and the 700 are about the same. I have seen 65 MPH on my speedo on both the 660 and the 700. I was also using my GPS when I was registering 65 on the speedometer of my 700 and the GPS recorded a maximum speed of 64.4 MPH (that was at around 5700 feet above sea level). I have never used the GPS on my 660 so I don't know how accurate it's speedo reading was. Acceleration-wise the 700 is quicker. A 700 King Quad can beat a 660 Grizzly in a 400' drag. But on the same strip the 700 Grizzly will take the King Quad...