And you don't think I have? I've literally built hundreds of computers and I've serviced and deployed tens of thousands of them. While ease of maintenance and installation isn't only a function of size, a cases internal volume is a big part of it. Out of all the cases I've built in, the larger cases are typically the easier ones to build in. Of course its not a 100% universal constant but generally speaking, it usually reigns true.
I don't doubt you have. But it seems to me that the ease of work with some larger cases is not causation but correlation. I've worked on small cases that were brilliantly easy to work on, while I've had full tower cases that were a nightmare due to idiotic design decisions, like having the MB tray so close to the edge, that you can't screw in the MB screws with a proper screwdriver because it is under the edge of the case opening.
Just because a case is large that is no guarantee that it will be easy to work on, and vica versa just because a case is small there is no guarantee that it will be hard to build in.
All things being equal, smaller cases with equivalent hardware will run hotter than larger ones. There are always points of diminishing returns and there are good cases that are small and bad ones that are large. Smaller cases are also much more limited with their cooling options. Not just fan placement, but radiator space in the case of AIO or water-cooled systems. You don't need to step up to a Caselabs case but in my experience, super small cases with really high end hardware run hotter than medium sized cases do.
Except all things are rarely equal. If all things were truly equal outside of size, the smaller case would not get hotter than a large one.
Most small cases are not designed with enthusiasts in mind, but I relish in the challenge of making them work.
Out of the box a typical small case will overheat with high end hw, especially with today's 450W video cards and 250W CPUs. But with clever modifications small boxes can be made just as efficient in cooling. It is not about the internal volume, but the amount and location of vents.
I'm not trying to give consumer advice here, if someone wants decent cooling for high end HW OOB they probably have to buy an enthusiast mid tower at least. What I'm saying is that the mid tower doesn't work better than a compact case because it is larger, but for other bells and whistles that come with it that help cooling efficiency.