block heater questions

[nonlinear]

i'm not a block heater expert, but from what I understand there are two types: an aftermarket, that attaches in the bottom radiator hose, and an OEM, which screws (?) somehow into the block (see below).

Can you guys tell the the relative merits of each type. i understand the aftermarket is cheaper and easier to install, but this will be an almost-new car and i really want to install the best heater so I don't hack the fuck out of it starting it for the next couple of winters.

thanks :thumbsup:

EDIT: and, does anyone know if the OEM heaters heat the coolant, or the oil. what are the advantages of heating coolant vs. oil. thanks.

[nonlinear]

aftermarket heater:

http://www.dieselgiant.com/blockheat.JPG

OEM heater:
http://z.about.com/d/autorepair/1/0/3/W/block_heater.gif

[Rat Fink]

.

[Bizzareo]

OEM style heaters are better, but if for some reason the car you have does not have a frost plug you have to punch a hole in the block, and you only have one shot at doing that correctly.