I do not agree with working with a small firm you can "learn" more.. This is merely a perception. Me myself intern with one of the big four and a small-medium audit firm. Both work load is the same. Just the seniors and the methodology is different. So it depends on your own. But i would highly suggest a big four firm for an entry in fresh level is better than a small medium size firm.

Let's say you join Chan & Lee Associates - a small medium size accounting firm. Then when after 3 to 5 years, you are bored with audit and you resigned hoping to look for a multinational company for an top accounting post. Here comes the dilemma for the multinational company. Say 2 people apply for the job. One is you and the other is from one of the big four. The multinational company will of course hire the guy from big four since it is the BIG FOUR rather than Chan & Lee Associates. So this is also the perception of the company.

Since big four and a small medium size firm has the same work load. Why worry? Go for big four if you can. Good luck and cheers!