My snow here in Colorado is not quite Utah snow but it is the closest thing to it for reference.
I started this season with a LT on a lazy enduro style FX450 and was so impressed how well the lower power transferred to the snow on the 450. We all thought it would be a DOG but it held its own with the FE570's all day long until wide open drag races. Then mid season I installed a ST on this same FX450 and the rev's came on faster and it became mor sporty. It was a go anywhere bike with the LT and then became FUN with the ST.
Now to your 300. I also have a MtnDoo inspired hot rod 2014 300XC with an SX. THIS BIKE IS THE MOST FUN I HAVE EVER RIDDEN!!!!!! I have been a lazy 4stroke rider all my life and had to learn how to ride a 2stroke. It is a completely different world. I have not ridden a 300 LT, but I would think you would have to be amazing on the clutch to be able to ride this setup and have FUN. The LT transfers the power so well it will load the motor all the time and not let that 300 run free with track spin in a way I like. I would recommend the ST for the 300. You will not have to work as hard to keep it in the power and it will feel much more like a birt bike with the ST, and that is why we build 300's. If we want to go any where we build Enduro style lazy 4strokes. If we want to blast through the trees with our hair on fire and branches sticking out of our helmets we build 300's.