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The 53-day period between Oct. 15 and Dec. 7 each year is a critical time for senior citizens. These dates mark the beginning and end of the open enrollment period for Medicare.

Though the regular monthly benefit payments received from Social Security probably place it above Medicare in terms of importance, the rising cost of medical care in the United States, coupled with lengthening life expectancies, could result in more being paid out in lifetime benefits by Medicare than Social Security within 40 years, according to research from the Urban Institute. Therefore, choosing a plan that's right for you could wind up saving you a lot of money over the long run.

Traditionally, most Americans (about 70%) choose to enroll in original Medicare. Original Medicare plans consist of Part A (hospital insurance), Part B (outpatient services), and Part D (prescription drug plan). Occasionally, seniors may choose to buy a Medigap plan as well, which helps lower their portion of out-of-pocket costs under an original Medicare plan.

However, an alternative to original Medicare is gaining steam with seniors. Medicare Advantage plans, known also as Part C, have grown like wildfire over the past decade based on data from the Kaiser Family Foundation. After just 13% of eligible seniors chose a Medicare Advantage plan in 2005, some 30% chose a Part C plan in 2015.

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Why Medicare Advantage plans are so alluring

Why is there such a draw to Medicare Advantage plans? The answer likely boils down to two key components.

First, Medicare Advantage plans are extremely easy to enroll in compared to original Medicare. Original Medicare may automatically enroll some participants receiving Social Security benefits in Part A and Part B, but it's still the responsibility of original Medicare enrollees to select a Part D plan or a Medigap plan should they choose. Enrolling in original Medicare is akin to pulling the puzzle pieces together each and every year. With a Medicare Advantage plan, Parts A, B, and D are often rolled into one neat package. Additionally, many Part C plans have dental, vision, and hearing coverage, which you simply can't get with original Medicare.

The other draw of Medicare Advantage is that it can provide a higher degree of clarity on your annual out-of-pocket costs. Original Medicare has no annual out-of-pocket limits for Parts A, B, or D, meaning if you have a chronic condition that requires frequent doctor visits or specialty medication, it could get quite costly. On the other hand, Medicare Advantage plans do have annual out-of-pocket limits for traditional Part A and Part B expenses. In 2017, this maximum out-of-pocket cost is $6,700, although you should be aware that there are no maximum limits when it comes to prescription drug spending.

You could also add in that consumers probably appreciate the choices and variation in plans offered by private insurers as opposed to the one-size-fits-all approach of Part A and Part B with original Medicare.

Beware of these hidden Medicare Advantage risks

But before you enroll in a Medicare Advantage plan, you should be fully aware of the hidden risks these plans carry.

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To begin with, because Medicare Advantage plans are offered by private insurance companies, their networks are often substantially smaller than original Medicare, which is accepted by 93% of physicians around the country according to a study by the Kaiser Family Foundation in Oct. 2015. To be fair, 94% of physicians accepted private insurance in KFF's study, but the survey didn't differentiate between the countless variety of plans offered around the country. In short, a Medicare Advantage plan is likely to have a much narrower network.

What's more, and building upon this point, insurers are within their right to alter their network on a year-to-year basis. This means there's a chance that your primary care physician could be dropped from your plan. This would be extremely unlikely to happen if you were enrolled in original Medicare.

Second, the time it can take to be seen by a specialist is typically longer with a Medicare Advantage plan. Since Medicare is so universally accepted by physicians and hospitals, referrals to see a specialist aren't needed. However, private insurance companies aren't too keen on paying the high cost of having their patients see a specialist on a whim. Instead, private insurance companies almost always require their Medicare Advantage members to get a referral before seeing a specialist. This can slow down the treatment process and add some out-of-pocket doctor visit costs in the process.

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Last, even though Medicare Advantage plans ensure that you won't pay a cent more for certain services, such as chemotherapy or dialysis, than you would with original Medicare, it doesn't mean you won't wind up paying more out of pocket for other services. As described above, should you need to see a specialist, you'll likely have to pay more out of pocket simply in the referral process. Medicare Advantage plans can also charge a pretty penny if you wind up getting coverage out of network.

Even with these hidden risks, Medicare Advantage plans could still be a smart move for some seniors. The key point is that seniors need to take the time to shop around and compare plans each and every year to determine which pathway offers them the best value. With roughly three weeks of enrollment still left, seniors have plenty of time to select a plan that works best for them.