I used to own truck hyphen graphics dot NET , something you just don't think could make money, but I built a suit that generated traffic, sold the s___ out of truck graphics via an affiliate program, and made a lot of money.
So, if that is your business model, to appear in the search engines, and count on type in and return traffic for zero, with no resale value to speak of, then you are always free to do as you think best. IMO, the extension is nowhere near the point where a hyphen is a plus, and I would stay away from them.
But, that approach can work. If it suits your goals, then build it, make a ton of money, and tell us all you told us so!