If the outs ratio is equal to or higher than the pot ratio (to use your terms), then it's basically an auto-call. This is given that you WILL win the pot if you hit your outs ofcourse, but in the case of flush or straight draws this is usually so.

For example, by the turn, the pot is $10, and you have a flush draw.. so 5.5:1 or something to hit the river. Opponent bets $2.. you have to call 6:1, so this is an auto-call.

Now let's say he bets $4. That like 3.5:1 to call.. so it's not an auto-call.. but if you think you can make some more money if you hit on the river, then you can consider calling anyway. Poker is all about estimating these implied odds, that is why I mention it here in conjunction with pot odds.