I think that the opposite is true (but depends on the type of connection). Mobile stations are focused on low power, they were designed that way from the beginning (e.g. they constantly try to reduce the transmit power if you have "too good" reception so it will be just good and use a lot less power) unlike wifi.

I remember the first mobile prototypes that were used around Motorola were dying of battery after few hours if used wifi instead of mobile data (that was about 8 years ago - so probably we are talking GPRS here).