Ive ran both and are both good kits but there are major differences.
1st off, both work great with cooler belt temps, making belts last longer, quicker throttle response and higher track speeds with the gear down.
Kurt's is a basic kit, easy to instal consisting of upper and lower sprockets, 2 belts (1 is spare), and instal tool. Spare belts are available for $129.95 cheaper than many Polaris dealers. You can see pics and details here:
https://shop.kurtspolaris.com/KO-GE...5&browse=-49755&shopBy=-14240&catalogId=-4127
TKI's kit comes with a tensioner, upper and lower sprockets, drive belt and replacement bottom gear bolt. Spare belts are only $80 and can be found at NAPA even cheaper.
There are 6 gear ratios available. The biggest difference to me is how many belt teeth are engaged with the top sprocket. With the stock or Kurt's you end up with about 5 or 6 engaged, with the TKI its about 15 engaged due to the wrap around effect of the tensioner. Because of this I have never lost a belt out riding with the TKI system. For pics and details go here:
https://www.shop.tkicnc.com/2016-2019-Polaris-Axys-26-Belt-Drive-TKI-BDP1626.htm
Both are great options and both great guys that I'm grateful are always looking to advance the sport. You cant go wrong with either IMO.