I prefer the hose heater in the bypass hose. Easier and more out of harm's way...
The heaters that splices into the rad hose is more prone to burning your car down if it malfunctions. The ones that go in the freeze plug has a much lesser chance of it.
I find they outlast the regular freeze plugs
SO CAL!?!?What do you even need a block heater for!? LOL!What is your lowest yearly temperature?? 45f?