I'm SURE this has been asked before, but I can't seen to find it in a search. I am a 6.8 nubie, so go easy.
My question is why does the 6.8 have different chambers?

6.8 SPC Chambers Available:

1: SAAMI / 0.05 " throat / akin to .223 standard
2: Improved SAAMI / 0.10" throat / akin to 5.56 NATO
3: DMR (only offered as a custom) / 0.08" throat & a 30 degree case to leade taper instead of 45 degrees / akin to .223 Wylde

I mean it's NOT a NATO round right? So why the different chambers? Shouldn't it be loaded to one spec just like all the other hunting ammo? It's also known that the Wylde chamber for the .223 is the best, so why doesn't this hold true for the 6.8? Everyone seems to want the Improved SAAMI.

Go to the AR Variants forum and look at the tacked thread about 6.8.  There's some discussion of the various chambers there.  I'm in the process of researching 6.8 for a deer hunitng rifle build next year.  I'm thinking Kotonics is the way to go, based on stuff I've read.  

There's only so much you can do with 30 grains of powder.  The longer throats and shallower leade angles reduce pressure.  Reduced pressure allows you to add a tad more powder.  The extra fuel boosts velocity a tad while staying within allowable pressure.  

Get too greedy and make throats too long and accuracy suffers.  

Another key distinction between NATO and Wylde chambers that you don't mention, NATO throat diameters are a couple of thousandths bigger than bullet diameter, while Wylde's are cut to bullet diameter, so while it still has a long throat, it's minimally sized so the bullet doesn't start off cock eyed.-

OK, I get it now. It all about reloading. I on the other hand do NOT reload. I used to, but now I'm an off the shelf kind of guy. So which chamber is best for factory loads?

I'm not sure, that may depend on the factory doing the loading.  IIRC, SSA had some loads that ran hot in early, SAAMI chambers but run OK in the Kotonics chambers.  Check out the other 6.8 threads for the skinny on that though.

That is a good question, I wonder what chamber Hornady uses for their load development?