Size DOES matters: jQuery versus Prototype

I just want to raise the fact that Prototype's size is an elephant comparing to jQuery. We are talking about 123KB versus 15KB here, which is more than 6 times. Most basic functionalities could be achieved by jQuery the same way as Prototype, and we are talking about this does not include Scriptaculous. I really eager to replace that in my Rails app, but it seems like that's not going to be that easy. If anybody could add something to me here would be definitely welcomed.