Funny that, I also logged in to ask someone to compare/contrast the same two pickups!
I have used the Boss, and had it not been in a guitar I sold, I’d use it for the harder edged blues rock that I sometimes play. It is fuller than the average vintage output Tele pick, fuller and punchier. It isn’t so far away from vintage that you wouldn’t recognize it as Tele.
Love the tunage, by the way. The Boss isn’t as bright as the typical low output Tele pickup. I like it for what I use it for, and it’ll work for me for harder edged classic rock type crunch too. Some nice grind, but still sounds like a Tele.
The Flat 50 is why I was going to come. I haven’t played it.
Just curious as to why you’re not looking at a Cobra or Piledriver?