For pads on a smooth rim the ultimate ones are original zoo pads but these are very rare. Someone was selling some on here a few weeks ago.
If not heatsink blues are a softer compound which is ideal for smooth rims, TNN greens are also exceedingly good on a smooth rim even though theyre compound is harder,
http://www.heatsinkbikes.com/?p=magura
http://www.tartybikes.co.uk/hs33_brake_pads/tnn_engineering_lgm/c4p10892.html