The simple rule
Hardware failures are repairs. Door failures are replacements. Springs, cables, rollers, hinges and openers are wear parts on an otherwise good door — replacing them is the cheaper, sensible move.
When replacement wins
- Multiple sections are dented, cracked or rusting through
- Wood panels are rotting or delaminating
- The door has needed repeated repairs in a short period
- Parts for that door are no longer available
- You want insulation, quieter operation, or a different look
The insulation question
If the garage is attached, has a room above it, or doubles as a workshop or gym, an insulated door changes how usable the space is and how much noise reaches the house. For a detached storage garage the argument is much weaker.
Ask for both numbers
Any honest company will quote the repair and the replacement side by side and let you choose. If you are only ever shown one option, ask for the other.