Such a list of "desirability" is kind of tough, since the "perfect" sled for any one person depends on a lot of things.
-Riding style(laid back tourer, aggressive trail, ditch banger)
-Riding terrain (groomed trail, ungroomed/break trail, some trail some off, boondocking, mountain/"steep n deep")
-Budget
and the list goes on and on.
Here's my "top 5" best sleds out there at the moment, based on "bang for buck".
1. Skidoo REV 600sdi (semi direct injection). Awesome rev chassis, bulletproof motor that's powerful and easier on gas. Expect to pay between $3500-$6000.
2. Cat F7. Wicked powerful motor, smokes a lot of 800's, F chassis is a close second to the REV, some argue it's better. $3500-$6000 or so.
3. Yamaha FX Nytro. The latest gen of the Nytros are much lighter, the 3-cylinder engine is probably the best on the snow, and Yamaha's finally got suspensions dialed in. $12k (new), to maybe a low of around $8k used.
4. Cat SnoPro 500. Rode one last year, it's a real fun sled. Racer replica so it loves to fly and the suspension rocks. Power is adequate, so long as you never plan to do much more than 70 or so. Not sure on prices of these
5. Skidoo REVXP with the 600 E-TEC. Talk about a smooooooth operator. Motor feels like it's electric. X-package handling is amazingly responsive. The early XP(08-09) chassis had a lot of durability issues, but the newest ones are doing better. Since they're quite new, prices are high.
You'll notice those are all oriented out of the box as trail sleds, with short tracks. It's possible to stretch pretty much any sled, but at considerable expense. Trail sleds are often designed with a set amount of clearance inside the tunnel, so getting a taller paddle track is not always possible, at least not easily. (Sno-x sleds are usually designed for a 2" paddle, as are mountain specific sleds).
The V-max was the trail sled (and the v-max 4 the lake monster). The Mountain Max was designed for, you guessed it, mountain riding. It had a longer/deeper track, wider skis, and higher handlebars(for stand up riding) with a grab strap. Otherwise I'm fairly certain they shared the same chassis and motors.
My find turned out to actually be the Sabercat 500, not the F5 (Firecat 500). Still a good buy at the price, but it's about 20hp weaker since it's the non power valve motor (80hp vs 100 in the Firecat), so a minor disappointment. Sharp looking sled though.
As I realized from my time with the 145hp Yamaha rocket sled, more power isn't always better. Unless you ride Canada exclusively, the power is more of a burden than benefit 95% of the time. Sure, it's a blast to pin it on a lake, but winding through trails, in fresh pow pow, or steep hills, and it's just too much weight to lug around. Most trail riding is in the 0-50mph range anyway, and you definitely don't need a R1 motor to handle that. If all I rode was the superhighway-like groomed trails in Canada, an Apex would be the
perfect sled since you can make use of it's awesome power. Otherwise....not so much.
Thing is, I now have a little more than half the power, and I'll still get down trails faster just because the sled is a good 150lbs lighter and far more maneuverable.
Heh....just for fun here's my top 5 worst sleds, based on experience.
1. Polaris FST. The FST is the "Four Stroke Turbo", or "Four Stroke Turd". Our school has one of these. It was such a terrible sled, Polaris actually gave it to us. Free. They didn't even want it. It's the generic Weber 750 engine with a little turbo on it, supposedly pushing out 150hp. I say nay, since my N/A 1000cc Warrior (145hp) blows it away like it wasn't even moving. It's one giant ball of turbo lag. The starter clutch has let go three separate times, each time requiring the motor to be pulled. Water pump shit the bed. Probably half of the 8 million sensors have gone bad, each time sticking it in "limp home" mode (which CANNOT be reset without the special polaris computer). Turbo blew the first time it got opened up on a lake. Handling sucks ass. It barely manages to squeeze out 100mph(the Warrior sails up to 115-120 before the FST hits 80). It's even heavier than my Yamaha. Sucks gas down like it's going out of style. Exhaust note sounds like a muffled whoopie cushion. Seriously, it's the closest to a genuine fart I've ever heard from a motor. Polaris likes to use carraige bolts on upside down surfaces, requiring a second person to hold the bolt in place while another puts the nut on. Polaris also likes to use plastic about on par with those throw-away "glad ware" containers for cowlings, with....wait for it....plastic carraige bolts that immediately strip out. They made a METAL bracket that crosses directly over the battery posts with no kidding about 1/4" of clearance. The battery also mounts to the clutch guard (so do half the sleds electronics), so changing the belt takes an hour instead of 30 seconds. The gas tank vent line is routed directly OVER the EXHAUST SIDE of the turbo, wrapped in a bit of tin foil. Our sled caught fire due to this, since if you fill the tank up, oh, I dunno, more than about 90% a bunch of it shoots out the vent line.
2. Polaris Fusion 900. These had a nasty penchant for catching on fire due to Polaris not realizing that exhaust pipes get hot, and a tin foil wrap on a vinyl line does not make it OK to lay fuel lines on the exhaust. They also ate gas like no tomorrow, and barely manage to keep up with 600's of any other make. A F7 will annihilate one...saw it happen.
3. Any old Polaris 440. Polaris' 440 was famously weak and shitty. Rode one and it barely managed to creep up to 60....my skidoo 380 would push 70. Then we were attempting to play around with it in some deep snow, which obviously required it to be pinned constantly. Almost made it up a mild hill and the chaincase went off like a bomb.
4. A 2008 REV-XP. The "new" REV had so many problems it wasn't even funny. They were banned from sno-x racing due to a defect that would cause the throttle to stick wide open, which happened at a race(hence the ban). They had problems with the front shock nuns breaking, the chaincases blowing up, and the tubs cracking from motor torque. Which was surprising since the 2007 REV was one of the best sleds out there and was famously durable.
5. Polaris RUSH. This gets on here because it's probably the most over-hyped and over-rated sled of all time. Woooo, it's got the shock OUTSIDE the suspension. Holy shit honey get the kids. It was billed as the ultimate ditch banger suspension that was supposedly impossible to bottom out. One of my friends got one so I took it for a ride. Suspension was decent, but nothing amazing. I would have put it on-par with a REV from 5 years ago, if not a little worse. I managed to bottom it out three times and wasn't even going that crazy with it. I'm maybe 190 in gear so not a huge fatass either. It's 600 motor was a joke. Weak weak weak, with a positively lethargic bottom end. I got it to 85 and it felt pretty much tapped out. My old '03 REV 600HO would top 100.