In my more cynical moments, I'm convinced that camera and camcorder manufacturers conspire to make buying decisions confusing by overwhelming us with unnecessary choice. Example: Canon currently lists 20 HD camcorders on its site, eight of which are 2011 models, 11 from 2010, and one is older. All are still available, and the overlap in prices--not to mention the $50 price increments--is enough to make your head spin.
Today's befuddling trio of camcorders in the $650 to $800 (list) range are the Canon Vixia HF M400, M40, and M41. They're pretty much the same, except the M400 has no memory, the M40 has 16GB, and the M41 has 32GB plus an EVF. So to figure out which to buy you must first decide whether you need the viewfinder; the screen is hard to view in direct sunlight, so I recommend it. But if you've ruled it out, you then have to figure out how much a 16GB Class 4 or better SD card will cost--it's about $30 at the moment, FYI. So if you can find the cheapest M40 for less than $30 more than the cheapest M400, get the M40. Otherwise, get the M400.
Still, if you've got to do that much research to decide among three products just from one manufacturer, before you even start comparing to competitors, there's something wrong.