Pros - Vintage tone without being muddy, not as pricey as some (TIs). Feel great under the fingers.
Cons - none
First of all, I am a flatwound strings fan.
I have them on 6 of the 8 basses in my collection (including my upright, which is kinda a given), and other than new flatwound strings I am trying out, they all have Sadowsky flats on them.
I've tried a number of flatwound strings from all the major makers.
These just tend to be the best of all worlds.
They feel great. Not low tension (higher than TIs), and not too stiff (my major beef with Chromes)
They sound great, both fingerstyle and with a pick (nice snap when played with a pick).
They are not the cheapest, but not the most expensive.
And they give you that sought-after vintage tone without being muddy.
Pros - SOOOOOOOOO Buttery. Makes your fingers feel like lightning.
Cons - (crickets)
Let me start by saying that I've never used flats on any of my basses, but I never felt comfortable with them when playing them on other peoples' basses.
My friend recommended La Bella DTFs for my MIA Fender P/J (passive) when I expressed wanted to use flats for a country band I'm doing. Bassstringsonline was back ordered, so I decided to try these instead. Holy God...I don't even want to put my bass down. The tone/tension/feel is pretty much exactly what I always wanted, without even knowing I wanted it. Actually, it sounds like the DTFs would've probably been too high tension for my liking, so this was a happy accident. At $42, why would you not?