I’m planning to reapply next year after being waitlisted by all the schools that I applied to. Do reapplicants have a higher chance compared to first-timers? Also, if you reapply to a school, would AOs consider your last year file as well or would they see you as a whole new applicant?
Depends on the school. SwimKid reapplied last cycle. Was admitted to 2/3 schools that he reapplied to. In thoese cases it helped I believe as it showed a true desire to attend. At one school we did not have to fill out a new application. They reopened the old one. However, he chose to reinterview, submit a new essay and send a lot of updated info.
I know one person who applied last year (to Exeter), was waitlisted, reapplied this year, and was accepted. Just anecdotal evidence, but it proves that it’s possible.
I reapplied and got in this year. Second Time’s a Charm!
As I’ve said many many times, the plural of anecdote is not data. If the OP wishes to reapply, then s/he should reapply and spend the next year doing things to make the application as strong as possible. I would not suggest overthinking this. 
Do everything you can to make your application stronger (after all, there’s a reason others were chosen this year)… but know that you will probably gain a couple of points among yield-conscious AOs who will assume that you will enroll if admitted.
Before making the decision to reapply, I think it may make sense to speak to the admissions to ask for feedback. Your view?
The probability of getting direct feedback from the university approaches zero. More likely the response will be along the lines of “So many qualified applicants for limited spaces.”
A good friend of mine approached an admissions officer of a school that his kid was rejected from. He did it in the summer, when it was quiet, and there wasn’t much activity going on. The admissions officer reviewed the file, and gave some good feedback.
I’m not sure if every admissions officer would do this for you, but it may be worth a try. It might be better if you asked your parent, or guidance counsellor to do this on your behalf.