I would still go for Acess & Safaricom on this one.
Being slightly expensive means they only get customer numbers that they can handle thus enough bandwidth for everyone. Zuku on the other hand is cheap thus will grow faster than they can handle.
Unlike zuku access is
REAL dedicated bandwidth.
If you used safaricom during the unlimited offer you must have noticed speeds were reduced by almost 50% why? Because the the consumers overwhelmed their bandwidth.
Moral of the story : If you are willing to part with a few thousand shillings you will save yourself a lot of time, stress and get really good speeds.