Originally Posted by
WhyFi
Some people, myself included, like to have some in-ride feedback. Having the screen on for that is a major drain. Besides that, phone GPS has never given me terribly accurate results (though I haven't used a phone for this purpose in 2-3 phone generations) and most phones aren't compatible with the Ant+ HRMs and speed/cadence sensors. I think that phones will close the gap even more (hopefully we'll start seeing more BT LE phones/peripherals, soon), but even so, there's something to be said for dedicated devices.
I use a dedicated cyclocomputer (an old Polar HRM) on my handlebars and keep my phone in my pocket running Strava. A 50 mile ride drains the battery maybe 30-40%. I always have it fully charged before doing a ride of any considerable length so that's no problem for me. I may pick up a small spare external battery for century or longer rides but those are few and far between these days.
As far as accuracy is concerned, my phone and computer report mileage within a few tenths of each other at worst. That's good enough for me.