I'd do a combo.
a lower rad hose is a great example... negates the need for afreeze plug heater.
if you have power steering or a loader in the way.. though the freeze plug may be easier.
a mag heater is not good for the block.. but is great for the oil pan.. slap it on the bottom.
can do so for the hyds and diffy if you like.
I have a buddy in indiana. has 3 mag heters. oil pan, trans and hyds, coolant heater, and a 1a trickle charger. he keeps them on a timer and sets them to come on about 2.5 hours before he goes outside.
leaves him a warm / topped off battery.. faster hyds, faster / less drag tranny and warm oil and water. cost him 100$ to do that. but pays off whenthe white stuff is on the ground I hear.