NTSC is usually the better option. Games play at 60 Hz, where pal versions play at 50Hz. Certain developers would optimise – or even develop game from the ground up – for PAL territories, thus giving a comparable experience to the NTSC game. There may even be games that are superior in PAL.
You can use Google to obtain a clearer and more detailed answer on the differences between the two standards, but NTSC will be better the vast majority of the time. If you’re a stickler for obtaining the best experience possible and have specific games on PS1 in mind, you should definitely Google. Otherwise just go with NTSC.