I tend to push towards concessions on lesser enemies instead of pointing out that they have less consequences...also when time is of the essence...
"You've made some pretty good arguments as to why the guy should leave the enemy and join you. If it's cool he's going to concede and tell you that maybe his boss isn't looking after him properly, and he'll consider what you said. If you want to win him over completely, it's going to take a few more minutes of conversation, and the biker gang is going to get further away from you"
"You've taken down three of the eight gang members... the rest are going to try to run, leaving their fallen buddies behind. Is it cool if we call that a concession and go ahead and move towards interrogating the one dude you left alive?"
On the BBEG, I tend to actually have valid escape plans (insta-spell back into the nevernever is popular) to use instead of trying to rely on concessions. So I approach the concession by giving the players something extra, like this: "Ok. here's the deal; the dude has a pretty reliable escape potion that will get him out of here. We can roleplay that out and he'll likely do so successfully without giving anything away, or we can just say that he concedes here, using the potion but accidentally dropping a piece of paper as he tries to scramble for the potion."
That said, because i was trying to teach my group how THEY could use concessions, I used concessions for bad guys consistently, even when it could have ended in death. The only time I didnt offer a concession was when the enemy was something unintelligent like zombies or w/e.