I have both the TC Triumph, and the Knight Vision. They are both good rifles. The differences are:
The Triumph (around $450 - $600) is a lot more money than the Vision ($330 - Blued version).
The Knight rifle is all steel, the Triumph has an aluminum alloy receiver. The Knight Vision comes in blue and stainless, the Triumph comes in blue, and a "weathershield" (silver colored) finish. I'm not quite sure, but it always felt like the Knight was a little heavier. The Triumph has a exposed hammer which must be cocked prior to firing, the Vision does not have an exposed hammer.
If you decide to buy the Knight Vision, I would recommend that you make sure that you purchase the version that doesn't use the red plastic (primer) jacket. I purchased the Vision that used the red plastic jacket, but I later purchased the "adaptor" that allowed you to just use a #209 primer without the red plastic jacket. I believe that Knight now sells the Vision in both versions. The Triumph has the "speed breech" feature, which to me wasn't much of a selling point.