[5NL] A7s...blind vs blind...limped pot...line check.

bet/(bet + pot) is useful in all gambling situations.

It is more generally stated as risk/reward.

If the total you have to risk
divided by the total that someone will win
is equal to your chance to win,
then it is a 0 EV gamble.

If your chance to win is greater than this ratio, then it is +EV to risk.
If your chance to win is less than the ratio, then it is -EV.

Raise or fold preflop, and it's not particularly close.

It's too strong to fold, so then we're raising.

You don't think he calls with worse bvb? 56, 67, 78,79, T8, T9, JT, J9, QJ, QT, KJ, KQ etc etc etc all seem worse to me! And this is very narrow bvb even. If he only calls better then you should still be raising preflop, because that just means he's folding way too much.