>>Slightly more complicated, is to take a bus or sherut to TelAviv and from there the 480 to TelAviv.
It is a fair bit more complicated, especially if you have luggage and don't know your way around. The bus or sherut from Netanya will NOT take you into the bus terminal. You have to make sure you are getting off at the right place because it is only one of many stops in Tel Aviv. (Anyone, the driver or any passenger, will tell you where to get off.) You then have to walk for about three or four minutes to the terminal from which the Jerusalem bus departs. It may be marginally quicker, but it is certainly less convenient. By taking the 947, you just have to get on in Netanya and not think about anything else until you get off in Jerusalem. It's definitely preferable for a first-timer unfamiliar with the route.
Oh yes, and bring on plenty more rain!