[richard in NC]

Originally Posted by MRichmond

With the same reasonably skilled driver, a sports car with less power will turn faster lap times than one of these SUVs. There always will be exceptions, such as if comparing very low power cars on tracks with long straights, and if the driver's skill is restricted to mashing the accelerator to the floor. (A Radical will demolish not just any SUV, but the Caymans and BRZs you mention.)

What is more fun is, I suppose, in the eye of the beholder. Having driven on track everything from high-HP SUVs and sedans to fully caged race cars, I think the latter are more fun because they allow the driver to improve his skills more. Also, having tracked and raced properly prepared cars with real safety gear, it is not nearly as fun blasting at over 160 mph into a hard braking zone with nothing but a helmet and a three-point seat belt. For anyone planning to make track excursions a regular occurrence, I strongly urge acquiring a dedicated track car. In addition to improving skill, the safety gear is absolutely critical and there simply is not a viable street-track car compromise with adequate protection (especially given how capable and powerful current models are). In addition, the cost of consumables (tires, brakes, etc.) is much less in a car that weighs less than 3,000 lbs instead of 4,500-6,000, and one in which the suspension can be dialed in with significant negative camber.

All good points but that doesn't take away from the fact that stock for stock, the X3M/X4M are quite capable on track in the hands of a capable driver.

Bringing up an example again, I witnessed first hand how good the X3M/X4M are at a BMW Performance Center autocross (big and open for an autocross course but not a full racetrack).
Experienced drivers with track prepped and even caged e36/e46 M3s and M Coupes were running mid to high 80s per run. My personal best in a stock M2C is 89 seconds. Mike Renner in an X4M with 3 passengers was running consistent 82s!!!!!!!! Oh, and with chicanes here and there, max speeds were 90 something for the fastest cars so it wasn't just a power/top end advantage.