Oh dear, you've opened a can of worms. The short answer is no system is better - both have their pros and cons:
PAL
Pros
[1] Increase resolution. PAL has approximately 20% more resolution than the same image in NTSC. Of course, HD-TV is starting to take off in America now, and PAL is vastly inferior to a HD-TV image.
[2] Better colours. This applies more to transmission than DVDs (and I think, in theory both PAL and NTSC should give the same colour values as long as you have an RGB connection).
[3] Smooth images. Because no extra frames are created when transferring film to PAL, rapid horizontal pans and other movement doesn't jerk.
Cons
[1] Films are transferred approximately 4% faster. This means a 100 minute film would be 97minutes when converted to PAL. This has little effect on the visuals or the pacing of the film. However...
[2] The soundtrack is also speeded up appromimately 4%. This means music is noticably different, and all sound is also played back at a higher pitch. This is something most PAL viewers don't notice, but a person who is not used to PAL transfers, or has musical awareness can notice. Some people who do notice the soundtrack differences say it spoils the experience for them.
NTSC
Pros
[1] All American TV shows are shot at 30fps. This means TV based DVDs of American shows are transferred in their native format. Converting NTSC to PAL can cause artifacts.
[2] Films playback at the correct speed, meaning soundtracks are the correct tempo and pitch.
Cons
[1] NTSC has lower resolution. Typically I don't notice this often will live-action films, but the difference does appear to be more pronounced on hand drawn animation based films, with PAL often looking vastly superior.
[2] When transferring a film to NTSC, the 24fps of the film has to be extended to 30fps for NTSC. This means every third frame is repeated (sometimes merged with the next frame). While this is to quick for people to notice 99% of the time, rapid pans can appear jerky, as can zooms and other large areas of rapid movement.
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It really depends what you think is more important. If picture is important to you, then PAL is often better (but remember, a PAL transfer can be taken from an NTSC master, which will negate all of the PAL advantages).
If sound is more important, than NTSC is better.
Of course, NTSC is often better as R1 discs are cheaper and available quicker!
