The reality is that M-Pesa is the preferred (mobile money) choice for many vendors. Many vendors/establishments accept just M-Pesa that one has no choice but to use M-Pesa.
I prefer using Airtel Money where possible coz it's cheaper BUT my choices are limited so I default to Safcom.
Greedy when others are fearful. Very fearful when others are greedy - to paraphrase Warren Buffett