Accounting Big 4 Internship to Full Time Offer

<p>Hey all,
So I have secured an internship with a Big 4 firm for the summer through
on campus interviews and enrolled for a one year M.S. program next year. Truth is I
wouldn't be so happy working there full time - I would prefer working in
a mid size firm (but I got rejected from the only mid size
firm that recruited on campus for internships in the past fall). My question
is how much time do the Big 4 give to accept their full time offer given at the end of the summer? Has anyone been able to delay it until December? I want to
participate in on campus recruiting in next fall and see if I can get a full
time offer at a smaller firm. </p>

<p>If I can't delay it that much, is it worth taking the risk by rejecting their
offer and participating in interviews again? Any other tips?</p>

<p>Also how would I be able to use my big 4 internship to my advantage when interviewing at mid size firms? How do I answer a question like "why didn't you take the full time offer with them? why us?"? Not to mention, the internship is in tax and most mid size firms focus on audit.</p>