I had a quarq for a year before switching to a Stages (I switched because I changed groups on my bike). With the quarq, my left/right power distribution was close so I wasn't worried about the Stages measuring left only. I'm happy with the Stages. I also like the way you don't have to use a magnet with it. I probably tore the magnet off the mount with my quarq three or four times over the year (pretty much every time I dropped my chain it would knock off the glued magnet). From what I can tell, the power reading is close between the two (and that's backed up by some of the reviews I've seen). Besides, I'm more concerned with consistency and it does seem to be consistent.