I received an RA offer for Phd from one of the mid-ranked schools a couple of week ago. The offer is signed and sent by the advisor and he had asked me to reply to it by the end of this month whether I'm joining his group or not. In the meantime, I received admission from one of the top schools in my field (electrical engineering), however, no decision about the financial aid is stated in their acceptance email. I'm now very tentative whether to accept the first offer or not. Because, there is a possibility of getting assistantship later and in this case I would missed the opportunity of getting into a top university. What do you suggets?