I vote for "rev match the clutch/flywheel". The synchros do their work when you push the gear lever into the required gear, before you start lifting the clutch, at which point the dog teeth are engaged.
The main reason for matching being that otherwise the tyres have to do the work of spinning the engine up to speed, in addition to gripping the road, which could push them over their limit of grip.
I may well be wrong though!