probably the way to go, but 'another thing to plug in' if you're building something for someone else to use

You need to plug in the headphones/speakers anyway, so it is just a little piece in between :)

this is true, but non-technical users (the likes of for whom my last pi project was built) get easily muddled!

Non technical users can get audio off hdmi i think.

not so convenient for "a box you plug into some speakers"