Like most things, it all comes down to how you plan to use it. I have two of these same size packs (not Kuiu unfortunately) but maybe my size experience can help.
My 1850 is perfect for the all day trip with enough of the basic protective equipment (fire starter, emergency blanket, water, flashlight, socks and a few candy bars) in case I got stuck out over night. With out modification, I have easily fit both tenderloins and a backstrap with all that in the bag to make it back out to the pack frame comfortably. I like the size, so I don't overpack, but wouldnt plan staying out overnight with just that size.
This is where the 3000 came in. For a barely noticeable weight difference, I gained an extra 1200 cubic inches to fill with.. tents, stove, food, sleeping back. All the essentials for one or two nights out. I feel like once I zipped the bag up, no way would I be able to fit much of anything else in to bring back out with me. Other members of my family use packs in the 4500 cubic inch range, and for the slight increase in weight over the 3000, can fit practically anything and everything they can carry. The 3000 is good as a planned day pack to bring out a good load or cape and horns, but I catch myself packing the extra's that I never really use. My next pack will be in the 4200ci range. Hope this helps.