Its really based on design. The SR is a perfectly square design, making it a good drift engine. It is suited for drifting because the piston bore is as big as the stroke. The bigger the bore, the more revv-able the engine is focusing on high rpm power. The KA on the other hand is an undersquare engine. I has a much bigger stroke than bore, focusing on low-end power. A turbo will pick up the slack pretty sufficiently on this. I posted a link a week or so ago on the limits. No set limits on it, but heresay is you can go 12psi on the stock pistons, given the engine is in good shape. I'm glad to hear the KA-T decision.
KA24DE-89mm bore, 96mm stroke
SR20DET-86mm bore, 86mm stroke
Oh and revving isn't everything, you also have to make the car move, i.e.torque.