The right question is never 'should I repair or replace my windows'. It is 'which components of this specific assembly have failed, and what is the least invasive intervention that restores documented performance'.
Work through it structurally. Is the frame sound? If the jambs, head, and sill retain structural integrity, replacement is discarding functional material. Is the sash repairable? Localized rail or stile decay is routinely scarfed with milled stock. Is the glass failed? That is an independent, inexpensive fix.
Replacement earns its place in specific circumstances: multiple frame members with structural loss, openings being reconfigured, or assemblies where the original construction was genuinely poor. Those cases exist and we will say so when we see them.
Cost comparison must include scope that quotes often omit. Replacement typically disturbs interior casing, exterior trim, and sometimes siding and drywall. Restoration does not. Compare the finished condition, not the line item.