fatfillup, I agree with you my friend. Hex dies will cut threads. As a distributor of Morse Cutting Tools, their catalog simply says, " Hexagon Rethreading Dies are used in repair and maintenance applications to repair existing bruised or rusty threads. They are not recommended for cutting new threads". They have a nice web site
www.morsecuttingtools.com, and also good inside sales support 800-255-1701 to answer questions.
You and I both know the hex dies will cut new threads. According to Morse, just not intended to. That is where the round's come in.
Tack's original post, looking for homeowner dies, I know he will save money with hex over round. And, no need for the sometimes bulky handle. But, I only know what they tell me, so I could be misguided. It is an interesting subject. Your post brought up good questions.