That only matters if, for some reason, your password is length limited. If your password must not be more than four letters long, then yes, choosing your tokens

That only matters if, for some reason, your password is length limited. If your password must not be more than four letters long, then yes, choosing your tokens from an ascii table has the highest possible entropy. (Example: WPA2 PSKs, shitty websites.) If your password can have arbitrary length (or arbitrary enough, about ~120 letters), you can generate a 128 bit password with dictionary words as tokens. Sure, the password will be much longer (factor ~6), but also much easier to memorize.