I used to use GHS Nickel Rockers and D'Addario singles, and was never impressed by tone. But then again I've only recently gotten into the whole guitar tone thing. Up until now, I've just been screwing around.
I recently strung up some Ernie Ball singles on my older guitar, and was immediately impressed with the tone with the wirewound strings. It has that sorta scooped mid-range - the best I can describe it - that I usually associate with George Lynch's tone (although I've seen that he uses Markley).
So, when I strung up my new Dean, I went and bought GHS boomers (medium) just to experiment. I liked the Ernie Ball's better.
Furthermore, I've also been doing a little more reserach into which types of strings are better. I can't find the link now, but someone compared the GHS Boomers to the Ernie Ball Slinkys. They basically said that the Ernie Ball's has better bendability and playability, but the GHS Boomers were more dependable, and lasted longer. Both, the comparison claimed, had similar tonal qualities.
I'll be honest, before I switched to the Ernie Ball strings, I didn't realize how much impact the strings had on the resultant tone. Boy, was it a major impact.
As for the comparison I cited above, comparing the Ernie Ball to the GHS Boomers, the GHS Boomers are much harder to bend in my opinion.
I'm thinking about stringing up my older guitar with Ernie Ball Slinkys after I replace the tuning machines - I have an old Aria Cat Pro, and the stock tuning machines SUCK - just to see what the tone difference is.