Why drive a Cadillac when you can get to your destination in a Chevy Mailibu?

Could it be that the Cadillac will last you longer, and be more reliable?

I think that this is very likely the case. The more expensive model is likely better in quality than the less expensive one. It is quite possible though that you are simply paying for the name, in which case you would probably be better off with the cheaper heater. I faced this same question when I was shopping for my front load washer and dryer. I had to choose between the expensive name brand, because I felt safer going a company that I knew built good quality appliances, rather than taking a chance.