In the games where stats cap at 400, (and really you're probably gonna be in the high 200s unless you're NG+ing), WLB is about the same as adding 200 weapon power to everything, and at 170 morale you'll take like 10% less damage than you would at 150.
But if infight and gunfight are around those give extra movement or range at the 4th and 7th levels so unless there's barely any stages left to get PP on I'd generally go for one of those breakpoints first even if it costs more.
This is all over optimizing like a few hundred extra damage before other multipliers so really do whatever.

If you're playing a game with skill parts instead that all goes out the window of course, work with what scraps the game throws you.