There are two reasons to take the plunge, he said. "One is you never know what health crisis is around the corner. The other reason is you have to know what the rules are in your state. Just because you need Medigap later doesn't mean you'll be able to get it."
Medicare Advantage plans can be cheaper, but it's important to read the fine print and shop around, Baker said. "You need to consider whether or not the co-pays will actually add up to the same amount of premium for the Medigap."
People with retiree coverage from an employer need to ask how it relates to Medicare since many employer plans work only with traditional Medicare fee-for-service, Baker said.
Paul Gada, personal financial planning director for Allsup, a Belleville, Ill., company that offers people guidance with Medicare and Social Security Disability issues, said he's a fan of Medicare Advantage plans, especially for Medicare beneficiaries with a disability.
"You can change your Medicare Advantage plan every year if you want," he said. "You can't necessarily do that with Medigaps. After the initial enrollment period, they're not required to take you.
"The limitation of the Advantage plans is they are not necessarily national in terms of coverage," he said. "They are generally regional."
Still, some Medicare Advantage private fee-for-service plans are more portable, which can be appealing to retirees who split their time between two residences, but not all doctors accept it, Gada said.
An 'Eye-Opening Experience'
The window that people newly eligible for Medicare have for making their initial selections in the program can seem long--it starts three months before their 65th birthday and ends three months after--but it's important not to procrastinate given the complexity of the job, Gada said.
"That first enrollment period is really an eye-opening experience for people," he said.