Any question answered...

Of course. Totally forgot about the Alfine. Thanks!
I have a 175mm crank at the moment, is that 5mm difference notable?
As you recommended it, does it get your Approval™?

5mm shorter cranks won't hurt you, even if you notice them (which most people don't, in blind tests)

I have two of them on the Tester Tandem. They are worth the money, if that's your budget, then that's my recommendation.

As I understand it the Alfine one is basically the same as a 105.

Alfine is nothing like 105, that's why it's half the price. It's more like FC-4600 Tiagra, i.e. not hollow.