Hi Rob,
Actually on my Fretless 6 I'm using LaBella Deep Talkin' Bass nylon flats. I think they're the sweetest sounding flats I've tried yet. Maybe the Bass has something to do with it as well!
My Fretted wears Smith Rock Masters. I find them a little aggressive sounding - but I got used to them. Besides, the purple silk they're wrapped in looks too cool with all that Purpleheart on the Bass.... But seriously, I do like the brightness and clarity. I prefer lighter gauges around 120 - 125 for the low B. At 36 scale, they're tight enough to go light gauge.
Rami