I have owned 2 Kimber Stainless Target 2's, one in 9mm and one in 10mm. I was very impressed with the quality and accuracy of both guns. I sold the 9mm and bought a Dan Wesson PM-9 and gave my 10mm to my dad for indefinite loan just because he loved it so much.
My dad has a late 1980s Gold Cup National Match and I've never been impressed with it. Compared to the Kimbers, the slide to frame fit is much more loose. It doesn't have a beavertail. The thumb safety lever is not very wide if you like to ride your thumb on top. The new stainless Colts have that matte finish on the rounded areas of the pistol. The Kimbers are matte also, but much more smooth looking and feeling compared to the Colt matte. Also, I've noticed that the matte areas on the Colt feel rough, like frosted glass, while the Kimber feels smooth. I also had a Colt Defender with the same matte finish on the top of the slide. It was really easy to develop rust if I didn't keep it wiped down with oil. Never had that problem with the Kimbers.
In terms of accuracy, there's no noticeable difference. I just got a new Ransom Rest for Christmas, but I haven't put both guns in to test them out. Really wouldn't be a good apples to apples comparison since the GC is 45 and the Kimber is 10mm.
Also the triggers will be different between the two. Both have a firing pin safety. Kimber uses a Schwartz-style that is linked to the grip safety. Depressing the grip safety releases the firing pin safety. The Kimber sear, disconnector, etc are not effected and will typically have a better pull. The Colt uses a Series 80 system where the firing pin safety is released through the trigger pull. I give Kimber the advance in terms of trigger.
You'll get a lot of comments here because the two brands are so polarizing. There's a HUGE number of people that think any gun with a pony on it is automatically a better quality gun. And there are a lot of people that think anything produced by Kimber is an inferior POS full of MIM parts that are as brittle as a twig and not worth anything. Figure out who the fanboys and haters are and take that information with a grain of salt. I've have both Colts and Kimbers. Both have their pros and cons. In this comparison, I'd probably go with the Kimber. But personally, I'd rather have an older Series 70 Gold Cup National Match that is blued instead of these newer Gold Cup Trophies or whatever they're calling them now. Give me a late 1970s blued Colt over anything they're producing now.