This input should have stayed PAL, as that's where the game was, and the NTS vesion is simply the same game without changes.
Here's the real guidelines.
1) if the game needed a NTSC-FIX, use the PAL version, unless the NTSC fix version was actually commercially sold. same for PAL fix (though generally ntsc is faster anyway)
2) if the game runs on both video standards without any difference except the slower framerate (and thus longer TAS time) then use the one that's faster (which is nearly ALWAYS NTSC) UNLESS the game was never sold in a NTSC region. (this is why i say this game is PAL, and should have stayed at that)
3) if there are PAL and NTSC compatible OFFICIAL releases, NTSC is preferred due to faster action.
4) if it's unclear, use the video standard that plays the music at the right speed, or the video standard with less graphical glitches. As an example of the former, bubble bobble plays some music at wrong speed on NTSC c64s, so it's a PAL game, and a run on NTSC not only shouldn't be accepted, it plays the intro story music way too SLOW. it may not be obvious what the right speed is, but when it's an arcade conversion, or has a cover of a real tune, it's obvious which is right. If the game flickers on NTSC and not on PAL, it should be ran as PAL.