Thanks for helping.
Still can't understand why everybody says FT over the Air is faster (suppose both are working correctly).
Taking into account:
Over-the-Air—The client communicates directly with the target AP using IEEE 802.11 authentication with the FT authentication algorithm. Over-the-DS—The client communicates with the target AP through the current AP.
So if my APs are hard-wired, why over the air should be faster?
This approach supposes that [latency to the new AP over the air] < [latency to the current AP over the air + latency over the wire between two APs]
Latency over the wire can be ignored as it is usually < 1ms, so we left with [latency to the new AP over the air] < [latency to the current AP over the air]
But not sure this will always be true, or at least in most cases... Interesting thing.