Actually they are not the same resolution NTSC-P is 480x640 and PAL-P is 576x720 so theoretically PAL-P would have better definition. This is based on my own experience but seeing as i have never seen an actual PAL TV I can't tell you for sure but I believe the quality difference is so small it's barely noticeable. Also remember that Standard Definition is region coded and High Definition is not. so 480i/p aka NTSC/-P is for mainly America, and 576i/p aka PAL/-p is mainly for Europe. I use mainly because America and Europe aren't the only places in the world.
So to sum all that up theoretically PAL wins when it comes to definition but there is more to quality than just resolution. Such as the refresh rate which on NTSC is 60Hz and PAL 50Hz
(Thanks Issac was trying to keep the answer as short as possible.)
720p and 1080p are HD resolutions and are not region coded