Should I repair my iPhone screen or replace the phone?
Repair it if the phone is otherwise healthy — on an iPhone 11 or newer the screen is normally a fraction of a replacement handset and you keep your data, your apps and your number. Replace the phone when several expensive things have failed at once on an old model, or when the board itself is damaged.
The case for repairing
A new front assembly restores the phone to how it was, and nothing on it is touched — no reset, no migration, no lost photos or messages. The screen I fit carries a lifetime warranty for as long as you own the phone, which changes the maths on keeping a two or three year old iPhone rather than replacing it.
A repaired iPhone is also worth noticeably more second-hand than a cracked one, so the repair often pays for part of itself if you do plan to sell.
When replacing is the honest answer
If a very old model needs a screen and a battery and a charging port, the total can approach the value of a good used handset. And if the phone has liquid damage on the board, a new screen fitted on top of corrosion just buys a few weeks.
In those cases I will tell you so. Selling someone a part for a phone that will not last is a bad trade for both of us.