It seems like you are pretty up on WiFi, so I won't go into all the inner workings. However, you did mention that the "handover takes ages."
The handover is handled by both the device AND a controller. There is a setting (and generally not accessible by users) at what threshold the adapter begins looking for another good network. It is taking ages because it takes that long for the signal to drop off. Once it does, your device connects to next available, strongest network.
Simply speaking, the controller helps with this process by monitoring signal strength of the connected device and then kicking off the low ones to force a rejoin.
Since those controllers cost mega $$$, it is much easier to just toggle Wi-Fi on/off. Setting your AP SSID is now just a matter of preference.