Ive used the ultra 3000 for years. Could get by with 1800 and save a few ounces but with spotting scope, binos, tripod, sandwich, raingear, puffy, kill kit, snacks, water, take off jacket it gets pretty tight in the 1800 when coming out or packing meat. Plus can do an overnight with the 3000. But on sale you can grab a bag for $70 so no biggie either way.