When we were looking for fifth wheels, we focused on those with the large basement. Many campers have a bit lower profile, with the step up to the bed area and a lower bathroom floor, which makes the basement much smaller.
Our Flagstaff has the bathroom/bed on the same level, which makes the basement much higher, and capable of storing a lot of stuff.
Add in all of the interior cupboards and the under-bed storage, and we have more than enough.
Plus, we opted for a long-box truck, so we could put a tool box behind the cab, which not only holds all of my tools and jacks, but also a bunch of camper stuff.