No it's not. Get the MyBook.
When it comes time to get another harddisk, what are you going to do.....buy another Time Capsule? Harddrives malfunction, harddrives get full. What if the wireless router starts to give you trouble in 2 years? You're stuck with a wireless router that isn't so great, and a harddisk that's trapped inside.
I think Time Capsule is great if you want to wirelessly back-up. If you don't care, and you don't mind backing up with the cable sometimes, then get separate components.