For many people choice is limited by coverage.
Richard Cox (richard@mandarin.com) writes
From my experience (including an independent user trial of the five main paging companies, in which I participated), I would definitely say that Hutchison provide the best service.
Bottom of the list, by a wide margin, was Mercury ... and second to bottom was Vodapage. I used to use Vodapage - but not now I have tried Hutchison!