2 years ago, one of my docs what having difficulty getting paid by the co. we had, and after fighting with them for a year, he finally quit accepting their insurance. It was Oct. so I paid the full bill and just change to a supplement in Dec. Well, I didn't know that everyone was eligible for the supplement when they first enroll but if you enroll in an advantage plan, you have to go through underwriting. I I have 2 medical problems. 1. severe back pain which i take tramadol for the pain, & 1. Neuropathy in my legs & feet that gives me balance problems so I use a wheelchair (NO MEDS!). I had a terrible time getting any supplement ins. Thanks to a medicare supplement ins. specialist, he found United Health Care through AARP didn't ask about wheelchair use.
I don't know WHO put that underwriter requirement in almost all plans, but IMO, it's BS! At the very LEAST, that info should be made prominently available to ALL new Medicare applicants.
Because of my experience, I would recommend that you go with a supplement from the getgo.