[quote]What sound are you after? Different flats won't all sound the same[/quote]
+1 on that, I have used several brands. Roto jazz flats were quite bright, I think thats down to how they are made. I found that the lighter 40-100 guage felt like a set of 45-105 rounds tension wise. I have also used Ernie Ball flats, not as bright as the Rotos but I found the guages a bit odd (heavy top's med bottoms 50-70-95-105). Didn't quite work on my jazz, not sure if it was the odd guages with the slim Jazz neck but the E & A were slacker than the D & G. I tried Roto tru bass strings a la Herbie Flowers, they were great on my Stingray nice m'wah sound but couldn't seem to replicate it on the Jazz. The latest set of flats I am using are Status Hotwires, I have a set on my Warwick (is that ethical?) and they are sweet. I play the blues and they are spot on for that. I have yet to get a set on my Jazz but I am very pleased with the sound they produce, the tension and feel on the Warwick. Of corse there are other manufacturers to try but I think I have found the ones I like with the Hotwires.