I'm door shopping for Moby's entry door. I bought one of these for the partition separating the bathroom from the rest of the box. http://tinyurl.com/clhsdb7
However, the more I look at it it, the more I think one of these prehung door units would be quite suitable for an entry door as well (available either as an inswing or outswing) because it's Energy Star compliant (polystyrene core) and faced in steel, e.g. conventional wood construction 'except' the facing material, instead of being luan or fiberglass, is baked enamel galvanized sheet metal so finishing is easy.
I'm thinking an outswing would suit my needs best (these have security hinges so removing the pin to gain entry isn't an issue). Anyway, it's available with single or dual bore and I'm thinking single bore because I'd install a dead bolt and pull it open using the key itself. This leaves the entire assembly nearly flush with the skin of the box.
Why would it be better to fork over $300+ for a real RV-type lightweight door (either square or rounded corners)? What important factors am I overlooking?