The "even frames" method of comparison you describe is flawed. Motion blur is very important to our perception of motion, and is the reason that motion at 24fps can look great on exposed film (lots of blur) and terrible in video games (no blur). When you skip half of the frames you have thrown out motion blur information that could have been present had the lower-rate source been created at that rate in the first place.

But yes, It would be neat to experience some legitimate side-by-side comparison of frame rates / motion blurs. Such a comparison has subtleties that make it hard to do fairly and cheaply.

http://100fps.com/how_many_frames_can_humans_see.htm (edit to fix small typo)