I've run both and you need to ask some questions on how you intend on using them before you decide on which is right for you. Here's my assessment;
Road - TKC - they run better on the road, are quieter, and have a better feel when heeled over. Karoo have a whine at around 60-65mph
Dirt - Karoo - both are very good but from my experience the Karoo did better in all around dirt. I'm not talking dirt road either. We're talking jeep trail, rock strewn, single track, and desert terrain and washes. I liked the traction and the feel feedback from the Karoo better.
Wear - TKC - neither should ever be chosen for their life but the TKC is good for up to 1000 miles more life than the Karoo. All use dependent. If you do any pushing, regardless of terrain, you can expect the mileage to deteriorate considerably.
Overall - this is where you really need to be honest with your intended use. If you are after the off road aspect then go Karoo. If you are after the dirt but will be doing a lot of road to get there go TKC.
What else? Ask away and I'll try to fill in
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