Epilogue to this…
I started this thread because my Gibson SG Bass with P Flats seemed to have a big volume drop on the E string, and the string felt floppy and undefined. So I ended up getting some LaBella DTFs for it.
The DTFs on the SG are just what I was looking for. I had a chance to play over the weekend at a church where I'll sit in occasionally, and the SG sounded massive through the house. The other musicians complimented how good it sounded. The feel and tension of the strings are great, so much fun to play. I feel like the strings gave the bass new life.
As for the P Flats, they got second chance at life, too. I ended up picking up a Gibson Les Paul Jr DC bass in February. Since I had the P Flats sitting in the parts bin, I stuck them on the LP just to help decide if I wanted to invest in some LaBella flats for it. Wow! The P Flats don't suffer from any of the weak and undefined E issues that I felt they had on the SG. The E seems really balanced in both tone and volume. Maybe just a little light in terms of tension, but they really do sound good.
It just reinforces the idea that there's really a dynamic between how a string and a bass respond and react to each other. And my Gibsons are happy now.