How did I miss this thread until now? Comparing this to the KSG seems logical, so I am suprised nobody has compared them beyond which one they want more.
Here is what I don't like about the UTS-15 compared to the KSG
The UTS-15 is slightly heavier than the KSG - roughly 137 grams according to the manufacturers, but with both shotguns in the 7 lbs range I see no reason to argue over 137 grams.
The UTS-15 is roughly 43mm (1.7") longer than the KSG - noticeable but not a night/day difference. Removing the flash supressor might shorten things up a bit.
The UTS-15 is taller as well because the pump does not wrap around the mag tubes like the KSG.
The UTS-15 is not ambidextrous at all while the KSG is fully ambidextrous. With semi-autos you would eat the empties if you fired from the oposite side the firearm is set up for; with a pump you could at least fire one round from the opposite side, but you would need to swith sides before cycling the action.
Loading: Top loading might be alright, but I do not like the idea of first lifting up a flap then shutting it again afterwards. I think the KSG wins here too.
Price: The exact KSG price is not yet known, but I am guessing it will be 40% less than the UTS-15.
Here is what I do like about the UTS-15 as compared to the KSG
The ability to go through 15 uninterupted rounds and alternate back and forth between magazines is nice. The KSG allows you to store a different type of ammo in each tube so that you can switch between them whenever you want, but I am not sure how useful this feature would really be.
Safties are an area I am neutral on between the two models: I guess this is personal preference - cross bolt for the KSG vs. non-ambidextrous AR style for the UTS-15. I would have prefered both models to be designed with an ambidextrous AR style safety like the RFB...
Kel-Tec KSG also can't fire 3" and 2.5" shells apparently.
Also UTS-15 without strike bezel, laser/light combo + iron sights is only 2.8kg