So I started off as a phone user and it worked great for me until I started going longer distances and using more features. Cyclometer on the iphone works great and even pairs with wahoo bluetooth speed and cadence sensors. Downside I had with the phone is:
1. It is big more so if you have a plus sized phone which can take up a good bit of room.
2. Display is difficult to read in sunlight, have to crank the brightness which kills the battery and still not great to see
3. Battery life is too short if you ride longer distances, sure you can turn the display off but that defeats parts of its usefulness. Also i want to know when I am 75 miles from home and have an emergency I have a charged phone to use.
4. UI - phone touch screens suck when you are biking, and if you drip sweat on it you might trigger things like pause by accident and not notice for 40 miles!
5. Durability - phones are the greatest for falls and water compared to bike computers.