My son is currently riding an upright 3 speed due to balance issues - post brain surgery.
The bad thing about the upright trikes is any cornering or side slope can be a tipping danger due the the high centre of gravity. I have to teach him to always approach slopes (even curbs) at 90 degrees etc.
It's working well for him to use to gain muscle strength and such, but I would not want to use it for any "riding" per say. Grocery getting etc. is fine, but that's really it's purpose in my opinion.

Also recumbents are more likely to be equipped with more gears. I'm not a bent expert though, so I'll let bent riders chime in on advantages as they see it.