I'm looking into buying a Bike computer and with the update to cycling in the workout app for the apple watch and with it's screen matching to the iPhone. Would the iPhone be a good substitute for a bike computer.
A bike computer is the mostly preferred way for outdoor rides. Battery life being the main concern as well as screen visibility under bright sun.
InDoors, a phone running something like TrainerDay / TrainerRoad / BreakAway: Indoor Training would be better/easier, But again, it's personal preference
But, just using the strava app on your phone.... even for subscribers its extremely sub par. For instance, youd think that a GPS based MAP APP, would offer the ability for turn by turn directions. But nope. Youve got to scroll around on your phone to try to find the upcoming turns. Its pathetic actually.
I find a bike computer to be much more helpful than just the phone. That said, be careful which one you get. I use Garmin and it has been extremely glitchy like, not loading routes (connection errors), taking forever to update to strava, etc. I hear people use wahoo and it might be a better option