Wow! This thread is covering some serious ground.
I think (if I'm reading things right) that what's really being discussed here is what makes the best all around small game head.
If you're talking every type of "small game" out there then there's only one answer and that's a sharp broadhead.
I'll knock the stuffin out of western red squirrels all day long with HTM rubber blunts and never think twice about it, but their eastern cousins will laugh at your best shot with a rubber blunt.
I've killed a pile of grays squirrels and fox squirrels with regular old steel blunts too, but I've lost a bunch with that head as well.
Some kind of blade is needed on them for "consistent" killing shots.
Midwestern cottontails go down pretty easy to a steel blunt or HTM, but there smaller cousins in south Texas run off with the same arrows from hits in the same places.
Jackrabbits of any discription are from another planet and require a broadhead or bladed blunt... I've killed a pile of those with steel blunts as well.... mostly the big whitetail jacks of Wyoming.
The thing I found that makes a blunt truly effective is it's striking surface. Make is bigger than the shaft for increased shock, dish the face to do the same and make sure the rim is "edged". In other words, the rim shouldn't be rounded or chamfered as that lessons shock and any cutting that might happen.
That is the main downfall of the steel nut used by some hunters... they are generally rounded so shock is lessened and little if any cutting happens.
Not to mention that they tear up softwood shafts pretty easilly when hitting hard stuff like oak trees and get knocked out of alignment as well.
As Vance mentioned I did invent the Magnus Blunt and am proud of it as a small game killer, but never intended for it to cost as much as it does. That pretty much puts it out of the picture for serious squirrels shooting.... it's fairly complicated to manufacture, hence the cost.
I'd love to see the Ace Hex blunt made in a slightly larger version as it has a lot going for it, but still not quite what it takes as an all around small game head.
For the most part as bowhunters, we must play a mix and match game for the quarry we pursue. If you've got the bucks or a line on a cheap supply of 3 blade broadheads you may just have the best all around small game head going.
Like Tom said above, you sure don't want broadheads spinning back to earth after glancing off a limb overhead, so they ain't perfect either.
I don't think anyone should use field points on any type of warm blooded prey. They have NO killing traits and it just ain't right to go after something hoping only to pin it to the tree or ground until you can kill it by some other means.