It seems the reviewer who wrote about Mai Khao, and other beaches near Phuket's airport, did not get to the bottom end of the island. It is 50 kilometres long.
Nobody who knows Phuket well would rate any of the northern beaches among the island's best. By far the best beaches - with the finest sand, clearest water and wide, gentle slopes are those on the Southwest corner: Nai Harn, Kata Noi, Kata and Karon beaches. Patong, too, despite the ugly over-development onshore.
Even the photo that displays with this review of Mai Khao is taken at the southern end. Mai Khai has no headlands or curves like this, and the water is never this clear. This is Kata Beach.
Mai Khao is very straight, though the real negative here is shape: the beach is relatively narrow and steep. At high tide there is little beach left, and it drops into deeper waters. When there are serious waves it can be dangerous to swim.
The real advantage of Mai Khao beach is the fact that it is very long, and there is hardly anyone there. And at the back of the beach there are more villages than hotels.