Lower radiator hose heater

Temperatures here in chicago have been brutally cold the past couple of days. My car, a 1999 nissan altima, usually sits outside all night. I don't have a block heater but was planning on getting one to install today as the cold weather is going to be around for awhile still. The auto parts store I went to had the typical freeze plug heaters but they also had lower radiator hose heaters. This type of heater would be much easier to install seeing as it does not require the removal of a freeze plug. The lower radiator hose is simply cut and the heater is spliced in between the two halves. The question I have is does this type of heater work as good as a block heater or is it a waste of money? Here is a link to the one I was looking at:

http://www.partsamerica.com/ProductDetail.aspx?categorycode=3057A&mfrcode=FIV&mfrpartnumber=14500

I would take a look at the wattage or amperage draw of both types. Although they are not 100% linked to heat output, they are correlated. The same wattage in the freeze plug is probably a bit more effective due to its location, but water is an excellent conductor of heat so either should work well.

The wattages of both heaters were very close. I would go with a freeze plug style heater but the easiest freeze plug to get to is behind the exhaust manifold, which I really do not want to remove. I also don't want to mess around with the freeze plugs if I don't have to as I always seems to have trouble with them. I do have another question though and that is does it matter that the thermostat on the car is in the lower radiator hose? I'm worried that it might prevent the transfer of heat to the block and that'll all get wasted going to the radiator.