The idea that the difference between an EP and an album should be determined by track quantity rather than by the total recording length, to me, implies that you have never listened to a band with a song much longer than 5 minutes. I think the distinction between the two is pretty unnecessary, really. Sure, if you don't have enough material to cram a record entirely full of music, don't just throw any old shit on there to make up the room, but honestly, what kind of band uses all the space available to them. I mean if your average pop band releases 25 minutes of music and calls it an LP, then releases a record that is 15 minutes of music and calls it an EP, but then a drone band releases an album that goes for 75 minutes and why is this still an LP instead of a third distinction? The difference between the first two is much less than the difference with the third.
It just seems really arbitrary, and although while vinyl is still produced, there is still some kind of legitimate need to have the term EP still exist, I think the definitions of what an EP is that people are coming up with here are entirely pointless and silly.
PS All argumentativeness aside, and using the definitions provided here, I usually prefer albums, because of their coherency and general tendency to hold together thematically better than an EP might, although if you can just put four fucking hot tracks on a CD and call it an EP, and charge half as much that is just as good for me.