Since this is an RV forum, I assume that the "AARP membership" being talked about is in relation to camping discounts.
From another perspective, we have had AARP's (most comprehensive plans allowed in our state) health insurance supplement coverage for years in addition to our Medicare coverage. Whatever medical care the DW or myself require - we walk out of doctor's offices and hospitals owing $ZERO - due to Medicare plus AARP insurance coverage in combination. We are AARP fans because of their excellent supplemental health insurance offerings.
Now .... with respect to camping discounts ... the most worthless campng membership we have is Passport America. RARELY do commecial campgrounds honor their supposed 50% discount - there's always some excuse at campgrounds as to why our Passport America isn't honored. What a waste. :(