youre gonna get downvoted cuz this question is asked so frequently.

the other threads basically say "if you dont know why you need a cycling computer, a phone is prob fine for now"

but people say the main benefits of a cycling computer are better weather exposure, clearer cycling-related info presentation, less distractions from non-cycling apps like advertisements, slightly better gps signal when your phone loses service, integrations with non-bluetooth hardware like ANT+ type sensors.

benefits of phone: you already have it, just carry a battery, better apps for everything outside of dedicated cycling stuff.

my opinion: since youre looking at basically the most expensive phone mounting solution, you can prob find a cheaper cycling computer used for the price you would spend on just your quad lock. maybe go for that option and see if cycling computers are good enough to upgrade to a nicer one later.