Again, I think you're right! Or at least that the frame rates are very similar. This is really interesting as I've didn't know that there were any N64 games that ran in true 288p with a comparable framerate to their NTSC counterparts. From your observations it sounds like the PAL version of Perfect dark does this as well (I didn't test it), but I wonder if there are more? I don't think this information is out there but it would be very interesting to know.
I did compare visually compare before, but the frame rates are pretty inconsistent in the area of testing (beginning of dam level) and I didn't check it thoroughly enough. You're right, the best way to test it would be using a frame rate analyzer like Digital foundry uses - but there's another way that's good enough to get the general picture:
I just ran the PAL and NTSC versions in the Project 64 emulator with Fraps on to get the framerate readout at all times. The emulator runs at the same frame rates as the console so you get a good general idea. I went to a couple of different places on the map and the frame rates were very very close in both areas when moving, turning the camera etc.
Diddy kong racing was different - I went on the first track and the NTSC version is generally locked at 30FPS and the PAL at 25FPS. Like I say, It would be great to hear if anyone knows if there are any other PAL games running at true 288p with framerates similar to the NTSC version of the same game. Perhaps Marshall would know?.