MO about the "old pro". It's not over for it yet lol.
Power wise the pro is easy to improve with the side benefit of better component life.
Gear down to a true mountain ratio to get use of the power available. The others have used this advantage to improve belt and clutch life over the last few years. Even though we don't "need to", for clutching, it still helps belt and clutch life and lower ratio pulls through deep and steep easier. I think some of the performance improvement on the Axys comes from gearing.
Different combustion chamber design offers power over the whole range and if your not pulled into the "higher ratio than your elevation needs", thing, helps with piston cooling-life too.
Polaris has been adding oil each year. Reasons are obvious but get it to the ratio of the others. Ads power by keeping things "like new".
Know your year. Poo has change fueling every year. Some are too lean here and there, some are too rich here and there and some are both. When it's right you wouldn't notice it so much but it will pull with the rest.
It's snappy and fun to use power. Most failures happen within 5 miles of a stop. Think that one through.
The handling is great stock. Best sled ever. Too many have been sold for just this reason to deny it but some want more. The platform is the easiest to move around on for room so for me "fit" was less important ie bar height. I see that as a good thing because rarely is mountain riding a constant terrain. I did find the front footholds tight so I opened them up to save myself when I screw up. IMO if handlebar height makes a sled something else is wrong.
Increased steering (decrease steering radius) helps the "Old Pro" as much as it did on the PC or M-sled and for the same reasons. Narrow front end or raising the chassis has the same effect but you don't have to move the bars as much to initiate. For this reason I always like to shorten the throw on the handle bars and increase steering and I did it to my Pro.
Suspension. MO ICR hit it when he pointed to QC on the shocks. I had no luck with different oil because bodies were too loose. Fade in 10 min. from expansion and wear contaminated oil in 200 km. EVO 3's were my cure because the stock shocks are so light anything else added weight but lots of good options including good stock bodies revalved. Shocks are huge even in 3 feet of snow because the sled still weighs more than you so why fight it.
Rear skid. You'd be hard pressed to measure the geometry differences between M-sled, PC, Holz and Pro skids with them on a bench. It's a good powder set-up. How they mount in the chassis is everything which allows slight rear shock control arm differences and front shock mount location. If a '16 Cat rear is better than an old pro skid it's only because of shock set-up or a couple of holes different and it won't be much different from a '12 pc skid with the front shock mounted a bit different.
Tracks are tracks so compare apples to apples in your world. Any bets on 3.5" before the end of the year?
Of all the sleds I've owned the Pro has the shortest list of must do's to make it excellent. I'm not excellent anymore but I can still appreciate excellent. If you need more than excellent, more power to you. If you want more than excellent, good luck because that is open ended.
The Axys will be more excellent than the Pro and the '16 PC Cat may be more excellent than the previous PC but will they be more excellent than the modified more excellent machines from last season is yet to be seen and more excellent can be improved to way more excellent if your heart desires (and many will) but way more excellent will soon be surpassed by way way more excellent so sooner or later you will find the level of excellence that you appreciate which may be more or less excellent than what someone else needs to appreciate excellence and it's all good because the level of excellence on the snow is still a balance of 90 % rider excellence and 10% machine excellence. Isn't it?
Or something like that.