Wifi would not be better from the technology side. If nothing else, the cellular radio technologies are built for devices to enter & leave their coverage areas with a minimum of disruption; the wifi/801.11 process for associating with a new access point is a gigantic mess and has never scaled well.
Quite happy about this! Wifi is great if you're walking through the station but quite hopeless when you're on a train.
I've found there have been many times when I've been sat at the front of a train and my phone has locked on to the first wifi access point in the station. By the time the train's stopped, this access point is now at the other end of the platform and the phone is still trying to contact it. By the time it finally gives up and locks on to the closest access point, the doors have closed and the train's pulling out. I've often found the only way to get wifi working is to manually turn it on when the train is about half way into the station. The phone then connects to the AP that's nearest to the front of the train and away it goes.
I've also had occasional problems with authenticating on the WiFi Extra network which seem to be station specific and intermittent.
The roll out of cell phone signal is fantastic; my phone just gets handed off between the cell outside the station to the cells inside the station seamlessly and away it goes. The only downside is having to listen to other people's phone calls on the deep level lines!