We have 10-speed on both our tandems, one Dura-Ace, one Ultegra. Both with SRAM chains. The only noticeable difference we've seen with the 10-speed chains is shorter lifespan. We've broken 2 chains, one 9-speed, one 10-speed...both Shimano (not at the connecting pin), so we're using SRAM exclusively now. We do enjoy the closer spaced gears of 10 vs 9 (we run 11-23 or 12-27 depending on the terrain).