I started to post yesterday, but I wanted to wait until I could play both whistles again first.
This is all in my own experience: your mileage may differ.
My original Feadog seems to have a stronger low octave but be harder to control. The Feadog Pro seems to have slightly less oomph in the low octave but is much easier to control in both octaves.
Is the difference in the whistles (Bloomfield's Pro and my own), or in the players? I don't know, but I do know that I like and enjoy the Feadog Pro a lot and that right now it's getting a lot of play compared to some of my other inexpensive whistles.
As to whether or not bad Generations exist...I've bought twelve high D Generations over the last maybe six years or so. Four have been wonderful, four have been just ok, and four have been unplayably bad (two bluetops and two redtops to be specific).
The bad Generations all have similar problems: they won't take a lot of air before the note just goes away; if you blow softly enough that the notes will sound, they have a very unpleasant rasp; and the low end of the first octave either won't play at all or will just very barely. My theory is that something happens, either in the molding of the fipple or in the assembly of the whistle, that makes the blade get out of alignment with the windway.
But I will grant you this: I haven't had to go through "boxes" of Generations to find really good ones. In my experience, if you order several at once, you've got a really good chance getting one or two gems, particularly if you order some of each "color"--get a couple of redtops, a couple of bluetops, and a couple of greentops.
Best wishes to all,
--James