Bigger is always better....at least with tank size
.
Larger tanks have more stability, and stability is extremely important when you need to medicate fish. Lets say you have to use an antibiotic on sick fish. A larger tank will have the better bioload capacity and can tolerate the hit on its biofilter better when dosed with antibiotics than can a 10.
I alway recommend at least a 20gal L for QT, unless you plan to QT very small fish only.
So, if you have the choice, go with the bigger tank.