I prefer the walk but I do take the bus on rare occasions. The bus leaves from C9, so if a C gate is involved with a number below or near that, you have a chance that the bus will be faster. If there isn't a line to get on it, it will certainly be faster. Otherwise you walk up to C16, go through the tunnel, then back through a third of the B gates to the T1-T2 connector. If you're starting from C1 it will be more than 10 minutes.