I have several 'Metrinch' spanners that work really well on rounded fasteners. But Snap-on called their stuff 'Flank-Drive', but it's several times the price.
I use 8,10,12,14 and 17mm size sockets on my Honda, but 6,8,10 and 13 on my R1 and KTM enduro.
Never have found a use for 15 or 16mm tools, except as spacers or tools for pushing bearings out.