It is easier to do the clutch replacement by removing the transmission; the hardest thing to remove are the bellhousing bolts and you would need to remove them anyway if you were pulling the engine. Pulling the engine also requires draining/refilling the radiator, exhaust removal (probability of broken off downpipe bolts), plus removal of fuel and vacuum lines, linkages, etc. AND, as Drone637 pointed out, the tranny weighs in at about 60 lbs, the engine at a few hundred.