What's the unifying element of our bible overviews?
Progress towards Christ
There's a massive difference.
If the spotlight is on the progress, a person might come away astounded at the themes they'd never seen before, the common threads, the disparate elements that now seem to have coherence. It's enough to make them really excited about the bible. For a good six months or so.
But it's possible to get excited by a plan and miss the Person. A system and miss the Son.