Space schmace. Just stack em
I like 8"--good for single-person stuff, or for cooking garnishes, toasting spices, etc, and they fit in the d/w once laziness takes hold (assuming stainless). Plus, for some things, there's a benefit to having things crowded in a smaller pan--prevents scorching, perfect size for potato galette, etc..
I think a lot of it likely depends on what you cook and how many you cook for. If you're going to be using a few pans at once, 8" stainless has a place. I also really like the little 7-8" vintage cast iron, and they work well for a lot of things, transfer stove to oven well, can be good to bake in--but mostly if you're cooking for 1-2 people... If you spend most time with one pan cooking, then 8" is way too small.
Regardless, worthwhile IMO to have an 8" stainless as well as a cast iron (if you're into cast iron). A calphalon is 15-bucks at Marshalls, so it's not going to break the bank to give one a spin and see if it fits your style/needs.