Knees shot? From what?
I think I'd choose salt. I've had enough mountains and the salt is new and exciting, for me.
35 yrs of damn near any activity can wear out knees or various other parts whether it be from work or play. Thats just life, but it certainly factors into the type of decision OP is contemplating.
Physical limitations brought on by age or kicking ones own ass for many years put aside...Id go woods/mountains over big water any day.
Thats just my happy place. The PNW would be a close second offering both, but certainly has its own trade offs.
Having grown up and currently stuck in the east(Midwest I guess is actually more accurate)
Ive been fortunate to travel quite a bit. For me, Ive never been on a trip to any coast that I wasn't ready to leave within a few days...save for Oregon/N.Cali coast, but that was a short trip.
Ive not made it to Alaska yet to have an opinion there.
The mountains though, I never want to leave everytime I get to them. The only reason Im not living there yet is its tough to find solid paying work out there to support a good quality of life for a family and realestate thats priced in the realm of reason close to that work.
It'll be different for everyone and thank God for that. If there was any one place that made everyone happy we'd be killing each other to get there and only the richest would be able to afford it...and they do anything possibly to keep the common folks out.
To the OP, It sounds to me like you currently have few limiting factors family or financially speaking so you have freedoms most dont in that regard.
I think the suggestions of traveling and spending chunks of time in places you are thinking would "scratch the itch" are solid advice. Then focus in on the one that you find fits you best.
I can relate to your geographic conundrum and wish you the best in finding the place that suits your desires.