Blocks fronting Ngong Road itself are noisy and dusty. Ask for a unit facing the internal courtyard, and check the water tank size because pressure on the Kilimani side drops in the dry season.
For this audience the single most important specification is water storage tanks. Nairobi Water's rationing programme means most estates receive mains supply on scheduled days rather than continuously. Storage is what turns an intermittent supply into a normal one. A block with undersized tanks will run dry on the third day of a rationing week, and you will find out in the shower.