I've found the opposite to be true. In a big company you usually have a strict role and responsibilities, know what and when to do, there are established proced

I've found the opposite to be true. In a big company you usually have a strict role and responsibilities, know what and when to do, there are established procedures for basically everything and if something unexpected happens, you know whom to call. In small, young (startup) companies you are forced to be jack-of-all-trades, take responsibilities depending on situation and there's nobody around to give an advice. Sure, it might be fun to be that-guy-who-keeps-everything-running when everything works fine, but when production server stops, you have no idea what has happened and nobody to call, all the fun ends very fast. Both ways have their cons and pros and my advice would be to try both, to see which one suits you best.