I have both kinds
 

In my various vehicles I have some of the OEM type and some lower rad hose heaters. The lower rad hose heaters are 600W and the freezeplug heaters are 400W. Given the difficulty of installation I would have a hard time recommending the OEM type. If you are already in there for something else then by all means put one in but as a job by itself it is hard to justify. As far as effectiveness I don't find either to be much better. When time comes for replacement the heater hose type has it hands down. There are also other types of heaters, circulating rad hose heaters with a small pump, nice but physically large, battery blankets to give your battery more oomph, stick on or magnetic heaters for your oil pan. Or self fired heaters like the Espar unit, though I suspect they would not work with Biodiesel as it has different combustion properties. Cheers Dan