Sadly they don't seem to offer a 38 Super commander barrel in the configuration I would need (standard/GI/Colt ramp). I wound up calling Kart and put in an order; they're a little more "old fashioned" in that I have to send them a check with my order on actual physical paper, but that's fine...I know what I'm getting, so I'm all good with that. Since they quoted me 6 weeks or so to make the barrel (they don't have any in stock), the extra few days for a check to make it there isn't a big deal for me.
Of those two, the only real choice for me would be Kart...Jarvis was also a consideration to be honest, but I liked the last Kart EZ-Fit (now Xact-Fit) that I did. I had a bad customer service experience with Barsto that I would rather not be put into a position where it might repeat. They may make a good and competitive product at a competitive price, but mistakes do get shipped out on occasion, and if you point out that their product has a problem and try to return it or get them to fix it if possible, you're likely to be accused of causing the problem yourself. At least that was my experience.