When building a delta, rear wheel drive trike you have two inexpensive options:
1) single wheel drive
2) "live" axle = both wheels fixed and dual wheel drive

and then there's the expensive option: a differential, allowing both wheels to drive but also to rotate at different speeds.

Basically a live axle drive will handle equally poor in both directions of turn, and due to the difference in circumference between the inner and outer wheel, one wheel will have to "scrub", slip & slide a little, fighting the turn and causing tire wear.