In terms of the CPU, A9 > Scorpion, clock for clock. At 1.2ghz, the Snapdragon should offer similar performance to the 1ghz Tegra 2. However, we're talking higher clock rate, and aslo larger die size (45nm, vs 42nm). So, I'd say similar performance with an ever so slight edge to the Tegra 2, as well as slightly better power consumption on the Tegra 2.
However, keep in mind the phones that ship with these. HTC Sense tends to be used on phones using the Snapdragon, whereas Tegra devices are used by other vendors. If you plan to go stock, a Sense-based device will offer a smoother feel than many of these other devices. I mean, the OMAP4 is an outstanding processor, but it hasn't stopped the Droid 3 or Droid X2 from being laggy as shit. But, if you plan to run CM7/8 on it, by all means, get the best hardware you can.