I have ridden both newer style and older style vectors. And I currently own a 08 IQ. I am 35 and I am an aggressive trail rider. And I sometimes have to ride in some pretty rough trails. Most trails I ride are tight and twisty.
IMO there is no comparison. The IQ is WAY WAY better than the Yamaha's. The Yamaha's I have ridden are tippy, they easily push, the rear skid bottoms out way to easy, and have way to much weight transfer.
Now before any Yammi guys jump me, I have ridden for many years, and know how to set up a sled. I revalved the rear shocks 2 or 3 different times. I bought a pioneer 13mm sway bar, I bought the big boy springs. I spend approx $1500 just trying to make this sled handle. I also cracked one of the skid rails, and Im not a jumper.
It at best was a decent slow to moderate speed cruiser. If thats what your looking for, then maybe you should test ride one of these sleds.
My current IQ, I added skydog skis(arent that much better than stock), I changed the RRSS to my liking, I loosened the front track shock, and changed the limiter straps one hole. All of this minus the skis cost me nothing. I wouldnt recommend the slydog skis. Stock werent that bad. I have 4500 miles on this sled and completely love it! It is the most predictable sled I have ever ridden.
So if you ride like I ride I would suggest the IQ.
If you ride slow and easy, pick either, though I will say, the Yamaha's tend to have more reliable engines. The Polaris 600 and 700 are great motors. Stay away from the 800. The 4 stroke Polaris seem to be good now too.
Just my opinion, and this is what works for the way I ride.