Question: I want an SSD SATAIII because to me it represents the best combination of quietest & fastest. But there doesn’t seem to be much choice relative to 2.5″ variants or non-SSD 3.5″.

I feel like there’s something I’m not aware of. Why are desktop SSD drives not commonplace?

Answer: It is cheaper to produce just one version, instead of two. 2.5″ variants can be used in laptops and desktop computers which makes them more flexible. The 3.5″ versions could only be used in desktop computers.

The technology easily fits into a 2.5″ case. There is no need to artifically produce a bigger case than necessary.