There have been many threads here over the years, appearing annually. As many sea service people do, I have accounts and products with both USAA and NFCU. Both have strong mobile platforms and understand deployments, PCS and other unique aspects of military life. Though I have ATM cards with both, I can use the USAA card at any ATM, any network, and get the fees refunded to me every month, up to a certain fee dollar limit/month. I have never exceeded that limit, so have never paid an ATM fee that was not 100% rebated. I think my NFCU card has to be used at a STAR network ATM to avoid fees, but I’m bit vague on that. NFCU has brick and mortar locations on/near most military bases, so I use the ATMs there. USAA has always been more online/phone oriented, and has very very few locations. Though I have been a member of USAA for over 40+ years, I can count on the fingers of one hand how often I have needed to actually deal with them in person. They pioneered being able to do mobile deposits from a phone app for personal accounts, and have focused on being tech-advanced and remote-capable.
NFCU has a slightly broader membership charter, allowing military members’ parents and siblings (I think) to become members. USAA has a more restrictive charter, as once the military person becomes a member, that person’s spouse and children, grandchildren, etc., can carry on the membership eligibility. Specifics for both are on their websites.
Both are fine organizations who cater to the military as their mission. I got both as an Ensign and have never used anyone else.