Compared to the fender, I think the Helborg set vibrates more freely. Tone is fuller and warmer to my ear. I think the 7150 is a hex core, but I don't actually know that. I think all DA strings are hex core. Please correct me if I'm wrong...How do the DR Hellborg Nickels compare to the Fender 7150s? I've always wanted to try the Helborgs.
Also, the pure nickel strings that come closest to 7150 are the La Bella Chicago Style Nickels, but they are a little brighter and not quite as tense. Very close though. Here's a thread:
La Bella "Chicago Style" Pure Nickel Rounds?
There's lots of good discussion of other pure nickel strings here, too:
Pure
Anyway I got into nickel alloy strings maybe 18 months ago, and tried a bunch. It's taken me until last week to get to the Helborg set. I'm really happy with them. Until now, I preferred the 7150 (because labella 52 alloy was discontinued).
I may never buy another fender 7150. The fenders are 4 string only with limited gauge and string lengths available. And while that's also true with the Helborg set, the DR strings -all their strings are 37.75" - fit on my 36" scale bass. And I can find a matching DR 5th string easily.
On top of that, these Helborg strings taught me that I am a fan of the round core.