I've both the clip and the S:Flo - both are pretty damn good.
I have the following gripes with the S:Flo - firmware, useless touchscreen, bad battery life, some audible artefacts, immediately noticeable sound smoothing (noticed this before ever doing RMAA tests)
I have the following gripes with the Clip: firmware is just okay, poor button layout, bad battery life, some hiss
I love both players for just sound (when they are in their element). The S:Flo IS more laid back - there is no denying it - but it performs certain instructions better: wider channel separation (closer to the CD), very little effect from hard to drive iems. The clip can be rockboxed and there is the real killer. It is easy to help it out PLUS enjoy gapless, REAL codec support, and in some ways, better sound.
The S:Flo is very good, but I won't be buying one. again, if it was smaller, had tactile controls, I could live with its faults. Both are good-sounding players. But personally, faults overall line up on the S:Flo.
That isn't to say the Clip is the be all end all - personally, it isn't. I prefer more stereo separation, gapless (Rockbox) and better codec support (rockbox).
But I understand why people like the S:Flo - but basing it only on SQ (or sound preference) takes the S:Flo way down in my books. It could sound like that for a LOT less and have fewer problems.