5 GHz WiFi signals are weaker than 2.5 GHz WiFi. While providing faster speed, it has a shorter range and is hampered by the relative weakness of its signal, which in many cases is unable to even pass through a wall without significant degradation. You might consider changing the location/position of either your MacBook and/or your WiFi access point (aka router).
2.4 GHz WiFi signals are stronger than 5 GHz WiFi. That's probably the reason your 2.4 GHz connection doesn't drop.
In my experience 2.4 GHz WiFi provides plenty of speed, even for streaming video. I've never had a problem with it,