Certainly don't do the one that needs to be advertised! When I said the plans were the same, I should have said the premiums can be wildly different for pretty much the same formulary.
I neglected to say that when I was comparing Part-D plans, it was through the lens of needing an expensive drug. I figured we don't need to do any hand wringing if it's a drug that won't hit the deductible. So I didn't get into price because, if your drug is expensive, all plans will cost the same amount, by law...the max out of pocket. The difference between plans becomes how hard you have to fight to get them to pay. Or how hard you have to fight to get them to accept a substitute if the one on the formulary has proven not to work for you.