I'd get a bike computer if it fit my budget. I'm surprised how essential the iPhone has become to my bicycling, although it sits in the handlebar pouch or my pocket -- I don't use a handlebar mount. I have no natural sense of direction and would get lost at every turn without some navigation aid. I even have a silly compass/bell combo and use the compass more often than the bell.

I've been using my iPhone 5c as a bike computer, mounted on my aerobars, for almost 4 years and I've never had a problem with vibration causing any damage to any functions of the phone.

For those that site battery problems when using a phone as a bike computer, this is a screenshot that I posted on another thread of one of my rides. It's from my almost 3 year old iPhone 5c with it's original battery. Connected to the phone is a RFLKT+, a Wahoo speed/cadence sensor and a heart rate monitor. If after a 3 hour, 50 mile ride you still need more than 66% battery life to make that emergency call you carry your phone for, than you should go with a Garmin or one of the other dedicated GPS bike computers.

You seem pleased with yourself in the way you make fun of people's interests. I bet you don't enjoy it when you're on the receiving end of that.

Cell Phone and Police Radio are always faster than a fleeing suspect ...

at this point, the sensor options for both protocols (ANT+ and BT) mean you can pretty much use either a phone or a bike computer. The phones have gotten a bit large at times for bike computers, otherwise, it's pretty much a horse apiece for functionality at this point.