Put the terms you need SEO wise in the slug. The permalink structure is pretty unimportant then. Better invest your time and money into content instead of finding the holy grail in permalink optimization. Unless you don't do all the time and adopt accordingly and integrate it into a whole SEO strategy, you won't get anything specific out of it.
But one criteria SEO wise is the speed your site will react now these days. So to say your permalinks should have good performance, so adding the ID is very helpful to give WP some speed. There's nothing wrong in having the ID part of the permalink these days, I wonder why this is not suggested more often (in the end it doesn't help with wordpress permalinks? :).