I tried the Kuiu Ultra 1800 and wasn't impressed. I ended up returning it. The frame wasn't comfortable for me packing a 50lb bag of cattle mineral in it for a few miles, just didn't fit me well. It was more uncomfortable than the J34 Eberlestock I have, and far more uncomfortable than the Eberlestock Mainframe. I have several Kuiu products I really like, nothing against the company, but this wasn't the right pack for me.
I've used Eberlestock packs for a while and still like them for several things. Their material is tough and quiet. The wide scabbard X3 is my predator hunting pack until the weather gets real cold and I have to pack more clothes with my giant Prairie Blaster FoxPro taking up most of the bag. I like the Mainframe and Superspike duffle that opens up wide and is quiet for packing really warm stuff into the whitetail blind in December. The J34 did a pretty decent job of everything when it was my only decent pack. The Mainframe with the right attachments for the job is really versatile, the next evolution of the Just One concept I think. When I got to packing more weight in optics and tripods around far more though I started getting daypack weights climbing to far over 20lbs. I don't like packing much over that in a daypack out west, and with 6-8lbs of optics and a 7-8lb backpack it was pretty hard not to. I decided to look at other options. My Eberlestock Mainframe weighs 4lbs 2oz after I trimmed a few things off I didn't need. The Transformer I tried still weighed 3lbs after I removed everything I didn't need so that option was still over 7lbs empty. The Little Big Top bag is heavier than that. The Spike camp or Supers spike camp duffle don't offer the organization I like for my optics. I have nothing bad to say about Eberlestock, their systems are all just heavier than what I was looking for now.
I was down to Kifaru or Exo with no option nearby to try either in person close to home. I have heard all the great things about Kifaru and own a Paratarp, Megatarp, and Parastove that have been great. I like Kifaru as a company very much and figure their packs are probably as good as everyone says. I'm also on Rokslide and listen to a bunch of hunting podcasts while baling hay this time of year, so I've heard a lot from the Exo guys. I've bought several things from Steve through S&S Archery also and he has been very good to deal with, so I have faith that Exo will be a top notch company to deal with also. I spoke to both Kifaru and Exo on the phone trying to figure out which is the best fit for me also before buying.
What made me go to Exo on this purchase over Kifaru came down to weight. I will be using this pack primarily as a daypack that can haul meat when necessary. None of the hunts I have lined up in the next couple years require packing in for 5 days, instead they will be from a base camp with day hunts. If it's to our advantage we will spike out a night or two at a time. For that I want a capacity of 2000 cubic inches plus and a way to carry my spotter and tripod where they aren't to hard to get to. I don't want a really heavy daypack, but want it to be able to haul an elk hindquarter out first trip.
The Exo 2000 shows it weighs 4.5lbs and the Crib attachment (for if I want to ditch the bag and just use the frame for meat) weighs 5.5oz. Total weight for the system is about 4.85lbs, and meat can be carried without the Crib at 4.5lbs.
The Kifaru version I was also considering was the 26" hunting frame with the Nomad 2 pack. That set up weighs 5.56lbs. Meat can be carried without the panel, but the Kifaru Cargo panel is another 1lb 11oz. All these pieces together were also more expensive than the Exo equivalent by $237.
The Kifaru Nomad 2 can grab a dry bag or other bag between the wings for more capacity, but the Exo can sandwich one between the frame and bag on the meat shelf to do the same. Personally any time I need more capacity I'd probably put a different bag on the frame anyway. If I like the Exo I'll likely buy a larger 3500 or even 5500 bag for it in the future before I go on a hunt where I need the capacity.
These aren't identical packs, the Kifaru is set up much different, but the capacity is similar. The capability seems similar also. I also don't think a person would probably go wrong with either choice, in my research I didn't find unhappy customers to often. I guess I'll know if I picked the right one for me when the Exo arrives. It seemed to fit my criteria the best, maybe it's light enough I'll pack the 15x binos more often and find more game.