Hmmm. I think many times the two words “fastest” and “most economical” do not go together.
If you are talking of fastest, for me and from experience, I will vote for Etisalat. If you are thinking of cheapest or most economical – of course the crown goes to Glo.
However, if you are seriously considering the network that can satisfy both criteria without actually being “both”, well I will say MTN fits that description.
I have never used Airtel so I cannot say where it stands when lined up with these ones I have mentioned.