In the long run what's the difference at RA? You pay for the Advanced and use your token on some other T5 later, or use your token on the Advanced and pay for some other T5 later. It still comes out the same in the end; especially since you can't use those tokens on T5 refit ships.
wanna save the token for the coolest ship ever, assuming I'm still playing by then, and it's likely the last token we'll get so I don't wanna waste it on a ship I won't like. thing is, and unless it's changed, the T5 advanced escort can only be had with a token. it's not listed for credits
You get a token at RALH 1 and another token at RAUH 1. You get a refit token at VA1. The VA token is different then the RA tokens. There's no point in saving it because FA1 will probably have a completely different token type as well.
The RA token won't work on VA ships, and vice versa. If you purchased the Defiant refit that used your VA token: you can only get that ship at VA.
Beyond that whether you spend 250k to buy a cool ship now or spend 250k to buy a cool ship later you still end up spending the same 250k. You can't save your RA token to buy a higher class ship later because each ship tier uses a different token.
But yes, ship tokens are Rank requirement specific.
A captain rank ship requires that use a captain rank token and only that token. You cant save a captain token and use it later at Rear Admiral. Nor could you use the Token to buy a Commander level ship
Vice Admiral token are used on the Refit ships. If you have bought a Defiant - Refit with a Token then you have used your VA token.