you should be prepared to answer the visa interview questions like: why change from working status to PhD; what's your career goal after PhD. Since you've been on H1 working status, I know it's hard to have visa officer believe you won't stay in the US after graduation from your PhD. But I think as long as you describe to them a clear picture of your career plan, they may even not bother asking you such stupid "stay or not stay in the US" question.
However getting a 10-year F1 visa once for a long period is not a bad choice if you really want to go back to China this summer. You should be fine. Good luck!
