Quills are not there for cushion. I'd imagine that falling on their quills feels like they are being stabbed. And say they fell on their head? It's happened. It's not likely that a hedgehog will roll into a ball in midair, either. Only some hedgehogs enjoy climbing, my girl never climbs and is not the least bit interested in it.
If you are using bar cages, there is a slight risk of falling also. However, it is not a very steep fall and the chances of injury are slim. Their limbs are simply too short to support all of their weight and they wouldn't be able to get up too far. You shouldn't use a tall cage anyway, it's length and width that counts.

I am against aquariums, no matter the size. I forgot to mention that when using sterlite tubs, it is wise to cut holes in the sides. Something that is not easily done with aquariums.

Granted they will sleep during the day yes, but if you want to take them out, most don't hesitate, at least none that I have ever owned, nor any of my friends.
MOST hedgehogs don't come out without at least a small "fight". It's in their nature. They are easily startled, as well. You can't say that Flower and Speedy haven't huffed at times when you opened the cage door or put your hands in..?

Chicken Soup, Innova, and Felidae do not contain the same ingredients. I consider Innova Lite to be a better feed than Felidae AND Nutro. I forgot to mention that you should try to use the Lite versions cat foods, if possible. The fat content should not be more than 10%.
Royal Canin may not be the best for cats and dogs, but I consider it a wise choice for a hedgehogs' mix!

Oh, and I still prefer water bowls.