The NPPL minimum is 32 hours, 10 of which are solo. You'll have to be very dedicated to do it in this time.
The full PPL is a minimum of 45 hours, again 10 solo, which is much more realistic.
The structure of the course is very different, NPPL you learn to fly, then take a GST, then you learn to navigate and do your QXC and take a separate navigation test. In the PPL there's just the QXC and a big test at the end.
The syllabus is practically the same, particularly for the first 20 hours or so, the NPPL simply allows less time for each lesson to be taught.
The NPPL is mainly aimed at people who don't meet international medical requirements but still want to fly as a hobby. If you want to take your flying further you really need the full PPL.