Satyrn
First Post
I have found this method to be more satisfying, too.I think they should be able to knock out an NPC instead of killing him. I just think that they should be working towards that goal in advance with all the limitations that goes with it. Instead of using a fireball, use hold person or some other spell that will incapacitate. Let me know that if you connect with your blow(remember that in 5e RAW, only the blow that takes you to 0 really hits), you will be pulling it so as not to kill the NPC. It's not hard to alter the party tactics to try to capture the enemy. Using those tactics IS the player having say in how things go.
My players have taken a quest (very much in the sense of taking a quest in a video game) to retrieve live specimens of various dungeon critters. Their corpses are acceptable, but of much lesser value, both gold and XP wise.
If I was using 4e's rule that a player m could make his fireball knock a skag unconcious instead of killing it, this quest's risk of accidentally killing the prize wouldn't exist. Indeed, one of my very few house rules is axing 5e's rule about choosing to knock out an enemy instead of killing it with a melee weapon. And since I'm using 5e's default assumption that monsters don't get death saves, they need to use nets, lassos, sleep spells and the like.
Like you said, if the players want to knock out something out someone instead of killing him "they should be working towards that goal in advance with all the limitations that goes with it." In my game, it creates a fun moment every time the player dares to swing a sword (softening it up for a sleep spell, say) at a monster they're trying to snag.