Ruaka is currently having Zuku blackout issues - no tv or internet signal for days. When it does come for like 20 min, speeds are 0.5Mbps. FTTH isn't there yet and they don't seem to be in a hurry.
Kinoo is borderline unsafe. My friends have moved out, some to Syokimau others to nearby Lower Kabete, both of which have water and FTTH. Syoks has 2 bedrooms at 25K, shopping mall is near, healthcare and the train 4x a day so you can plan to get home easily. Lower Kabete has 3 bedrooms for 30K, is easier to get to town, the air is better but it is colder and the schoolkids noise might become bothersome
Ruiru is far. The morning traffic jam will inconvenience you. Don't know about it's FTTH status.
Here is the speedtest for Lower Kabete
Airtel doesn't have a strong signal there so the mi-fi router won't work. You'll need FTTH.