The surgeon - s/he is actually a qualified doctor so their work is more relevant to you as a prospective medic. The point of work experience isn't to observe operations, you can watch videos on YouTube if that's what you're curious about - it's to gain an appreciation of the work that doctors do. You can't really do that as effectively if you're shadowing a PA.
Surgeon. They do ward rounds and clinics too so you won't just be in theater the whole time. Overall I think shadowing a surgeon is a great insight into the medical profession.