The 101 is definitely prettier than I-5.
Going up I-5, you would need to cross the Grapevine, which is a tough tow.
If you take the 101, you'll have a big grade after you get out of L.A. before you get to Canejo and another one after San Luis Obispo (the Cuesta Grade). There's also a small grade between those two in Gaviota. Don't let your nav send you over the San Marcos Pass. You'll hate it and everyone on the road will hate you. It only shaves 20 minutes off the drive for a passenger car--not worth it.
You can avoid the Canejo pass if you're coming in on the 10 by taking 210 > 118 > 23 > 101. This avoids a lot of city traffic too.