Matt Cutts is so funny. Pretending like this isn’t an important question by falling asleep. And then say one looks spammy. You card.
Do what makes sense and is easy for you and your users to navigate. Same goes for sub-domains vs. folders. If you have a good reason to run a subdomain then you should do that.
He does giveaway the real answer, long filenames look like spam. Folders are easier to organize /products/hammers/acme/pounder.html and code. The only reason to write a long html filename is to add keywords. It’s inelegant to say the least.