(I added to my OP.. had a bad habit where I post a little and then keep editing as I think of more things lol, sorry!)
But the main difference is the regular dee bit is a consistent size, it doesn't taper off as much as the hunter dee where it starts out a bit thicker and goes thinner. Also the metal may be slightly different. Some metals are heavier than others, some have copper in them, some are silver, etc. But I cannot tell from this bit.
As I said in a different thread, the same kind of bit from different brands or a different model, are all a little bit different. And it's that little difference which your horse may prefer or despise. You just have to trial and error it :P
"Strength is the ability to use a muscle without tension"