I own the Rubicon and the GB. Opinions....
I've already fallen in love with the GB. A great knife in every way, without the ability to tell you what I think over time since I just got it. But it feels good in hand, albeit a tad heavy as it is intentional designed as a work knife to stand up under hard use. My only real complaint is that I like to have some sort of finger stop to keep your fingers from sliding onto the blade. This one is minimal at best. Love the blade shape and M4 is one of my favorite blade steels. This knife is a looker, well built and will certainly do the job. Of course, M4 is a little corrosive and will require a little upkeep from that perspective. Not a big deal if you live in a dry climate and keep the knife protected. I use Tuf-Glide on all my knives in M4 (or other corrosive steels). Seems to work well.
The Rubicon is a special knife indeed. A bit costly, but I have more expensive knives that are not its equal in terms of F&F. Wonderful flipper. Smooth as silk. The knife is gorgeous. Pics just don't seem to do it justice. A bit "chubbier" than I'm used to, but that works with this knife. The roundness helps fill the hand and it is comfortable and light. Some people have complained about the steel choice (S30V), but that is one of my favorite steels as it gives a great compromise between edge retention and ability to sharpen as needed. I absolutely love everything about this knife.
If you have any questions about the two I own, I'll check back in a few times tomorrow and try to answer them for you.
I'm not likely to buy the Tatanka as it seems just too big for my taste, so I have no practical opinion about it.
My choice? If you don't mind the cost - buy the Rubicon. It is truly a "custom" knife at production prices.
Best of luck on your decision.