I transfered from H4 to F1 on 2001 at Mexico. I don't know whether it is still valid or not after 911. Personally, I think F1 is much better than H4. The most important thing is that you can apply OPT if you maintain your F1 status for more than 9 months. In this job market, OPT means that you can accept the job offer immediately without waiting for annoying H1 sponsorship. Good Luck!