For me, it is quicker w/out the clutch. With the clutch you let off the gas for a fraction of a second before pulling in the clutch, take a fraction of a second to pull in the clutch before shifting while still off the gas then you remain off the gas for another fraction of a second while releasing the clutch. Without the clutch, you only use 1 of the 3 fractions of a second listed above. Doesn't sound like much but IMHO, it is noticeable. At the track, you can hear the difference between the two. Clutchless, you're quicker back on the gas.