There’s a major thing about being freelance/independent : you are alone. Oh, you may work with a few freelance fellows, maybe a sub-contractor, etc… But you are in a one-man operation. No one to dump the responsibility for a failure, no one to save your ass if you screw up, and no one to defend your interests. As a side effect, you share nothing of the glory or rewards either.
When you have a client, he tends to work with you as he would with a company that has the same order of size as his own. If he runs a small operation, he can relate to your problems very well. He is generally kind of “lax” in terms of business relations, giving you more time if you need it and letting you have some room to maneuver. And you tend to be the same towards him : you give some space, you are more tolerant towards “it’s just a minor modification – but it takes a day or two to implement” stunts, etc… All in all, you are on equal footing, and therefore more relaxed.
And then you have the “much bigger” companies. I’m not saying that it applies to each and every one of them, but usually, the more people you have, the more diluted the power is, and the more consensual the internal decisions have to be. When you ask something you think is simple, be prepared to wait for a week to get an “official” answer. Oh, you’re not badly treated, far from it. But they work with you the way they would work with another “big” company. And big companies are less reactive, have more momentum, and way more financial inertia too.
Working for a big company as a freelancer makes everything more challenging, from getting the specs to getting paid in a timely fashion. But, and that’s a big but, without experience, you both think you are on equal footing : generally you talk to just one guy, and tend to think of him as the one who will take the decisions and get the answers. Sometimes it’s true. Sometimes, he’s just the visible chunk of the iceberg, and the iceberg can be awfully big, and slow.
If you start as an indy, make sure you don’t try to move too fast with these companies… you will loose your strength very quickly, and they won’t like having to understand why you act like Speedy Gonzales, or an enraged mosquito. Play by their rules. It usually is worth the effort. And if push comes to shove just remember your crash helmet, and use it well.