Yep speeds on Cellphones can be crazy fast, I was testing a WIFI connection speed with a cellphone. Data was quite consistent ... until I noticed I was on 4G. Only to get lower results when I turned 4G off (the WIFI there is slower).
Same experience as well, 4G has consistently been better then my WiFi connection. And even if i had perfect WiFi Connection i was still limited by Internet connection speed. Which most WiFi Connection spot, even at home, are slower then 4G.
I must say I have had the opposite experience. My home wifi provides a consistent ~100Mbps unless I go to the other end of my apartment. 4G, where the signal is good, goes up to ~20Mbps.
I'd say the problem is latency/routing. Any data on data?