Both have good and bad points
Dive bottles need filling from time to time,are bulky, need an annual safety inspection,but a doddle to fill up your pcp.
Hand pumps are lightweight,fairly maintainence free,but not cheap(£70-£100) and using one is like an hour at the gym! HARD WORK!
It depends what your using your pcp for,if your always at the range get a dive bottle,if out in the field controlling vermin, get a hand pump.
Ideally get both if your pockets are deep enough!
Hope this is of help
Jim