I've had both MP-10 and Tunze 6055 (pair of them actually). The flow is different - more controllable with the MP-10 but more directional control with the Tunze 6055. I ended up going with the pair of Tunze just because I liked the direction and the simple dial and set it.
For those small of tanks I would go with one Tunze (MP-10 might be overkill for the price, but if you're going up grade or you just like the "no cords" might be worth for you).
Both are solid and reliable though. Shouldn't regret either purchase.
I agree that even for 20gal, MP10 might be an overkill.
No experience with Tunze, but I am using Sicce XStream SDC for my 30 gal. It can be controlled by proprietary app or via IOTA, by Apex.