I tried to sample a bit from the three restaurants listed for Pleiku (also from a fourth that I happened to pass). In all honesty, they seemed about the same.
Same deal: A heaping plate of rice. You point out which dishes you want to try (many of which rely on mock meat), they add those to your rice and give you a small bowl of brothy soup as well. All for around 15,000 D.
Now personally, I don't eat much mock meat, so the reason I preferred this place to the others was because they seemed to have a wider selection of "meat"-less dishes.
That said, I don't think you can go wrong with any of the veggie restaurants you'll find in Pleiku.
Cons: Same as every other veg place!