I would probably First, answer the question - How often, how many, how wide, and how fast you are going to need those dovetails.
I have used two Sears brand, and the Leigh, and cut my own manually.
For production work, down and dirty, fast- go with the Leigh (longer initial setup time - high start cost)
For occasional cutting - the Sears ( I have both the old 20" and the newer 12") - fairly quick setup time - moderate start up cost.
BUT, for the best old triditional looking "craftsman" 'tails - I will hand cut mine- both self satisfying , and a good joint says something about the craftsman. It will also make you appreciate the labor our ancestors spent on a fine piece of furniture.
(Oh, I almost for got, hand ones can be adjusted "on-yhe-fly", something the templates have a harder time doing)
Hope there "ramblings" give you something to think about.
Mac