If you're considering getting your first boat, I would suggest not complicating the purchase by looking at steel boats. If you don't already know plenty about steel boats, you probably don't know enough to find happiness buying one.
Fiberglass is your best bet. Nothing's perfect, but fiberglass is pretty much the best thing going for recreational boating.
Problem with steel is corrosion. Build a steel boat and it starts rusting before you can even apply the primer. Stick it in saltwater and watch the fun begin. Constant vigilance is required to own and maintain steel.
A survey by someone who knows steel would be critical. The boat may look fine but can have areas in it's hull that are THIN.
Another problem with steel is weight. They're heavy, and prone to being slow, particularly in smaller sizes like 30 feet.
If you're in love with steel and have to have it, then proceed with caution. If you're considering a particular boat that happens to be made of steel...don't.