i will second this, won't really notice the difference compressed down into day hunting mode, but will be beneficial when hiking in/out, and offers more versatility. i have the 3500 for my K2, but doing it over again, i would just get the 6400 for versatility even though it will be a day pack more than a 5+day bag, they compress down well, with such a small weight penalty going to the 6400, would be an easy choice for me.I'd go to the 6400, it only weighs 2 ounces more, costs $25 dollars more and gives you about 1700 cubic inches more space than the 4800. The thing with these backpacks is that you can cinch them down to compress unused space, but once they're full, there's no way to make them bigger. Another option would be to purchase the K3 bag of choice and attach to your existing frame, should be a simple swap. I was looking to purchase a 6400 bag to swap out my existing 5500 bag and the general consensus here was to keep the 5500 and upgrade the belt on my K2 to the K3 belt.
The straps on the K3 bags are wider than the K2 bags, they'll work just take some fiddling to get through the buckles. I've got a 5500 and 2000 myself. May wait for the next generation to get another one. I don't NEED a new pack but....I'd go to the 6400, it only weighs 2 ounces more, costs $25 dollars more and gives you about 1700 cubic inches more space than the 4800. The thing with these backpacks is that you can cinch them down to compress unused space, but once they're full, there's no way to make them bigger. Another option would be to purchase the K3 bag of choice and attach to your existing frame, should be a simple swap. I was looking to purchase a 6400 bag to swap out my existing 5500 bag and the general consensus here was to keep the 5500 and upgrade the belt on my K2 to the K3 belt.
I was in a similar spot. I went with the 4800. I don’t think there is a wrong answer. However, if you are sticking with 2-3 nights, a 4800 is a tad cheaper and will be great for that purpose. I also like the horseshoe access. I can get 5 nights in my 4800 but I have a lot of really light, packable gear.I'm looking at upgrading from my Mystery Ranch Sawtooth with about 2800cu in to the k3 4800. I will probably keep the 2800 for a smaller daypack option and eventually a kids pack, but would it be worth it to go all the way up to the 6400 for 2-3 nights? I think I like the horseshoe zipper layout of the 4800.