I put an aftermarket soft "cab" on my 2014 x900. It came with doors which mount on hinges rather than the zipper things. I already had the plastic roof and glass windshield. I also use a golf cart propane heater.
The good: It blocks the wind. The doors can easily be removed in warmer weather by simply lifting them off. The propane heater works well--can work too well sometimes. You do stay dry in rainy weather--well mostly.
Not so good: Still get a lot of air infiltration when it is windy. I never did figure a way to easily block air flow coming in under the hood and under the dash--the "firewall" is open under the dash. There are open areas in the upper rear corners--the kit design left openings there. Of course the doors do not seal well either. This coupled with the openings mentioned above contribute to some rain intrusion, but it's better than no doors.
Also, I do not remember where I ordered the kit from, but will attempt to look it up. I should have the installation instructions around here somewhere.
As I remember, I thought the cost was fairly reasonable at the time. Definitely beat a hard cab price.