When I started out in the mid-70's, like most here, Entwistle, Squire, Greg Lake, etc. had this tone so different from the usual big round flatwound tone that I was intrigued. There weren't 40 or 50 string makers then like now, and these Rotos from England were something new and exotic. You really had to work at that tone in a world full of folded 18's and amps that were definitely voiced for that thick flatwound tone.
I remember at first it took a while to develop the callouses to survive them, and we all marveled at the rumor that supposedly they'd void a Ric warranty as they were too hard on the frets. Well, what the hey, these MUST be bad to the bone and I gotta have 'em !
I later transitioned to GHS Boomers as I could get them cheaper and went through a period of custom gauging them, which was easy with GHS, as most music stores had that wooden box with all the strings separately available, a big luxury back then.
Over the years I've come to lean towards nickel roundwounds, as the stainless are a little too much for me generally. I keep thinking I'm gonna try Progressives or some of the ground-wounds, but never seem to get around to it, and generally stick with Boomers or D'Ad XL's. Over time I've tried everything from Black Diamonds to TI's, and always seem to come back to those two.