I just drove a 19' 900T Renegade Adrenaline for a 75mile demo ride this past weekend. I need to make a decision for a Spring Check on a new sled this year and it's between the Renegade 850 or Renegade 900T, in either an X or XRS package.
I have over 25k miles on Ski Doo 1200 Renegades (2011 & 2016) and about 500miles on my wife's 900 Ace, since 2011. Before that it was all 800's... and rebuilds.
The 900T does everything better than my 1200's, all be it a colder ride for sure. Would need to add a larger shield/deflectors etc.
The handling on the 900T was very precise and easy to steer and the motor pulls as hard as the 850's I've ridden to about 80mph. I'm sure with a mild tune, the 900T would cause the 850 fits in drag race, it that matters to you, it does not to me.
I'm very comfortable with the ITC throttle, as I have it on my 16' 1200 and 16' 900 Ace Blizzard. In sport mode it was very aggressive and had great pull. I found "standard" mode to be preferred in the tight twisty's and sport mode just about anywhere else. It would behoove you to get a ride on one if you have not tried the ITC throttle, as I know many folks who absolutely hate it.
The G4 is very comfortable to me and the wider seat on the 900T was a little nicer than the 850's I've ridden.
After riding both the 850 and the 900T, I have to say the 850 is just a more fun riding experience and I can't believe I'm saying this right now, but I think at this point I may go back to an oil burner. I hope I don't regret it as either sled is really nice. If between now and April 14th, I decide to not go back to a 2-stroke, the 900T in my eyes in the nicest 4-stroke trail sled on the market today. It does not have near the power that the Yamacat 998 has, but it sure felt lighter and more flickable in comparison from my perspective.
Good luck with your decision in going 4-stroke.