The best option for you would be to avail for one; however, if you are pursuing both then the last action rule would apply in your case. The last action means whichever status you obtain last would dictate your status. For example lets say you got your OPT extension after the H-1B approval then you are on F-1 and not H-1B and vice versa. If you get your OPT extension first then do make sure to ask your employer to withdraw your H-1B approval right away so you can remain on OPT/F-1 status. .