I am a TASer, and I have been using the PAL version of lemmings for my MD/genesis TAS. The PAL version of lemmings actually runs 10% faster than NTSC on this console, whilst NTSC has a higher frame rate, the physics of the game updates every 3 frames in the PAL version, and updates every 4 frames in the NTSC version. So it would likely be best to use the PAL version for your runs. The PAL version is also a bit easier to find online (which is the reason I started using it back in 2017)
I wrote a bit more about it on the forum I write about my TAS in https://www.lemmingsforums.net/index.php?topic=2425.msg89912#new
Super cool information, thank you so much for sharing! I got a GEN and was thinking about working on that run after I finished NES/MS-DOS stuff, so glad not to put to much effort into a NTSC run (dont' see myself having a PAL console anytime soon).
Did some further experimentation and found the in-game clock is also affected by this 10% speed difference, i.e the NTSC game-clock runs 10% slower than PAL along with everything else. So if you want to go for purely in-game time, then the NTSC version will be a bit easier.
That's odd since in SMS NTSC clock runs concurrently faster but lag affects PAL less as the game has more time per cycle to execute.
