Funny, I've never head of Telo before, but I'd trade the rear cab for more bed length. 6' is a good length where you can fit a lot more things.

The Telo has a fold down rear wall to extend the bed. The Slate looks like the wall can be removed in SUV mode, less convenient to do so however.

Oh that's actually nice. Though in Slate's defense, they are trying to be the cheapest car possible so I'm not sure they're direct comparisons.