The SK, TF-1 and TF-2 eliminate the 2-3 shift overlap, firm up the 1-2 and 2-3 shifts , provide more fluid to the front clutch circuit, and gives a bypass to prevent excessively high fluid pressure during cold weather starts and higher RPM service. The TF1 adds down shift control for the driver. Firm, properly timed shifts eliminate slippage of friction material during shifts. The slippage of frictions is what wears out a tranny. The TF-2 provides the firmest quickest shifts and additional operator controls. The Tf-2 does not cause shifts that are severe but "firm", acceptable or even desirable for all except Aunt Mabel and Mrs. Clever who think they should not feel their nice little car shift at all.
If your going to the effort of installing a shift kit, i say, put in the TF-2!