Originally Posted by cobere
Always reraise KK preflop and hope to show it down so in the future you can occasionally reraise T9s and take it down.
I do understand what you are saying about sometimes calling, but I don't think this is a good spot. The primary reason not to flat call here is that it lets the blinds come in relatively cheap, like pgil said. If they both call, you're in a bad spot, so in this case you're reraising to isolate, in addition to all the other reasons.
If perhaps you had KK in the BB, and nobody else called the preflop raiser, you could flat call for deception purposes, but I would still reraise most of the time for value.