Yep, with travel insurance you have to be careful. Many places sell travel protection and not travel insurance. Travel protection is not covered under your State's insurance commission and is not as good as travel insurance.
But as you mentioned, each travel insurance company is different, so it's important to do your homework. Your agent can be invaluable in this situation. And don't automatically assume the biggest name is the best. In fact, we use to sell insurance from 5 different companies, one in particular is one of the biggest names in the industry - we had to fire them because their customer service sucked!