Best pack

Not sure on an exact model but badlands packs are very well made and comfortable! Plus their warranty can’t be beat! Kafaru packs are up there in price but from a buddies experience with them, very comfortable and warranty and service are top notch as well!
Elk hunting... usually in mountainous terrain. You'll be gone all day and it's not unusual to get back well after dark. A fairly big bag that can be collapsed for day hunts and comfortable frame that can be used to haul meat when needed are good to have. There's tons of packs that fill that bill but the best are probably Kifaru, Stone Glacier and Mystery Ranch. I have a Stone Glacier 6900 Talus that collapses down to a good size for day hunting pack and it works great. I hunted out of far less expensive packs for decades that got the job done too, so there's a lot of wiggle room in pack selection.

The best pack can feel horrible by day 3 if you don't get in reasonable shape to elk hunt and a so-so pack can be just fine if your muscles are not aching.

Anyway... the best are Kifaru, Stone Glacier & Mystery Ranch.
I have no experience with the above mentioned packs. I do know that every time this question is asked those 3 packs come to the top. The other one that seems to get a lot of love is the exo packs. The one that I have used and do like is kuiu. It is light and seems to be fairly comfortable. It works well for me as a day pack then if you get something down it will handle a quarter pretty good. Also after 3 years of pretty hard use had a part fail. Didn't render the pack useless just didn't work as it should. Got ahold of them and they sent me a hole new suspension system pdq. With their apologies for the inconveniences. Don't know if this helps. Good luck on your hunt.
Backpacks are very personal. I have tried Kifaru, EXO, Seek Outside, Kuiu, Eberlesock, and Stone Glacier. The SO, EXO and SG were the most comfortable. I am currently using the SG because I prefer its bag. I have broken two Kuiu frames so I will not use them again.
My thoughts are this.... I’m going to carry a internal lightweight frame pack as my day pack because I don’t want to waste a trip back out X amount of miles and elevation to get a pack frame. To me that’s a waste of energy and a load of meat. I first bought a Kuiu 5200 pro setup. I absolutely love the bag and thought I loved the frame until I bought a Kifaru. Now I use the Kifaru frame with the Kuiu 5200 bag on it. The Kifaru frame has endless adjustments with is what works for my fit fat contour and the Kuiu bag has a great selection of pockets that work for my gear. I carried in one trip 2 back straps, a front deboned leg and my 5x5 head and cape off my elk about 1.5 miles straight down with the Kuiu frame and it held up fine. I also train with 80 pounds in my pack during the summer and the Kifaru carry’s it far better with less felt weight.
Best pack? Most comfortable? No such thing in general. It is like asking what the most comfortable shoes are. Try some from the above mentioned and find the one that fits you best.
Packs are a very personal thing and just about everyone has their own favorites. The brands that keep coming to the top are all excellent by reputation and all of them should do the basic job (carrying your gear in and out, hopefully with lots of meat on the way out). I limited myself to good brands, and then tried the packs on. I want something that fits well and can put around 75% of the weight on my hips as my first check box. The second check box is that the pack has the features that I want (rifle/bow carry system I like, pockets well organized/sized for my gear, things like that). I won't buy a pack that I can't try on in the store, and preferably try with some added sandbags for weight.
I have an Eberlestock Just-One that I use for hunting and it works well for me, but that doesn't mean that it will work for everyone. For regular backpacking, I have an Osprey Atmos 50, and I have a Gregory Zulu 35 as the daypack that I use for work. I use the same criteria to pick those packs too. That Atmos 50 is extremely comfortable, and if it wasn't orange I would consider mounting a rifle scabbard and using that for hunting too.
Basically, decide what your specific needs and criteria out there, then find a pack that meets them. All of the brands mentioned in this thread make good quality packs, so if you are looking at them it is just a matter of finding one that works for you.
EXO!! Hands down. Great company and get to speak to the head guy as many times as it takes. Finally made the jump. Can't believe the difference. I had a diablo for ten years that is great for warm light hunts. I noticed some of the other packs makers copying the exo designs. Thats flattery and a good idea.
Look for a 70 liter pack that weighs less than 5 lbs. Osprey has a new pack like this.

My old 70 liter Dana Designs Terraplane pack weighs 7 1/2 lbs.! That is a ridiculous empty pack weight. Eberlestock pack, while of excellent design and construction, are way too heavy. OK for military use but not for hunting and general backpacking.

Gregory makes some light, large packs as does Granite Gear and several others.

Eric B.
I had kifaru, now Mystery Ranch, Metcalf and Marshall. The Metcalf is perfect. It’s the Nice Frame one. I find it to be way more comfortable than the kifaru was. Dana knows how to make a pack!!
I do want to try out Seek outsides packs. You can change the stay length by adding sections and they are pretty lightweight packs and waterproof.