H1 extension sounds better, detail inside

H1b extension will give you another 3 years and have nothing to do with your 485 approval. Besides, it cost less, since EAD has to be renewed annually.

EAD could be risky, once your 485 is denied, EAD is out right away.

Another consideration: for those funding agency, they will understand H1 visa much better than EAD, whichi is depended on 485. The later is just too complicated for most 'normal' Americans.