LaBella flats on my SG gave me the perfect classic 70's rock tone. Thin Lizzy, UFO, Sabbath - just loved 'em.
Also tried D'addario black nylon tapes (nice Beatle's Sgt. Peppers tone) and short scale round wounds by Ken Smith (strong mids with bite - similar to Rotosound 66) and D'addario XL-160 nickel rounds (bright at first, but mellow in 12 hours of playing to a nice round tone).
If you need the bass to be versatile and cover a few different genres (rock, metal, blues, jazz, country), then I would recommend the D'addario XL-160. They have the broadest range. But if you just play classic/hard rock, I don't think you can beat the LaBella 760 flats. They are just magical on the SG.