I would have to disagree with a lot that is said above, just make the comparison to big mountain skis, are they shorter or longer, they are longer, a longer track gives you better float, it side hills better and easier and the suspension works better. The 175 is the easiest sled we make to ride, if it was not no one would ride it, who would ride a sled that could not turn, would be heavier etc, no one. The fact that we sell a ton of them shows that most have an idea about them that comes from the past, every machine today regardless of brand are easier to ride so you can't take the past and use it to drive the future.
Also saying that a skid is garbage just shows that you have not spent time on these machines, and saying that some people could ride them but most could not? Actually I said this in another forum but the stock machine with ski-doo is designed to give the largest amount of riders the best in all conditions. So if you only ride in the tree steep and deep like the video of Chris Brant then yes the polaris does that better until you change the settings on a ski-doo to match the polaris, to do this suck up the limiter strap by one and stiffen the rear end to the stiffest settings, if you are a bigger guy use a stiffer spring, now the sled will react just like a polaris in the steep and deep trees, however it will be harder to initiate on edge like a polaris is and it won't carve like a ski-doo anymore, so if you want to do more powder turing then you will want it changed back, if you want both the limiter strap adjustable accessory is something you will be buying. The hard thing about these forums is guys use them to tell or show everyone that they are super awesome riders, this maybe so but that does not help everyone else by having to specific change the snowmobile and especially spend a lot of money. If you are a rock star then the things you do specifically might not help the general average good riders. I am always skeptical of anyone who says it is crap and they act like they have done all the testing, when the truth is often they went with something and actually did not testing, they just believe it is better, testing something takes a ton of time and having the same sleds set up differently in the exact same conditions. Takes a lot of time and money and most riders don't do that as they want to ride. As I say, I am not the best rider but I can hold my own and most guys who see me throw around a 175 are pretty generous saying the can't believe a guy 5'6 140 pounds can turn that thing. It is all about technique and just riding, not thinking something will be hard because it is longer or bigger.
What ever sled your looking at, just get out with the dealer and ask to try the two sizes back to back, then you can make the best idea for you. And personally if you rode a 154 in an xm well then the 165 is is pretty much the same and 16 the 175 is the same, were not taking huge length changes here were talking one paddle on the snow.
Again to show my point most guys wanted the 154 3 inch and they say they want a 154 because it is light, it turns quicker, faster track speed and then they say they want a 3 inch which actually negates all the things they used to say they need a 154, the 154 3 inch is the hardest sled to ride in the line up as it has so much traction that it just wants to wheelie and once the skis go up, the sled is not flat and it goes along at an angle trying to get back on the snow, hence why so many guys get stuck or dig super huge trenches, you have to be a quick on the draw sledder with wicked throttle control to combat this action. Or you use all that stated above and lose your ego and get the 2.5 track which will allow the 154 to almost stay with a 165 3 inch, it also gets up flat easier due to the spinning track quicker and getting up not trenching down. We have a lot of guys now going back to the 2.5 for this reason. Just try it and you will be amazed how much better it is...