Nintendo Switch ownership costs are often driven by controllers rather than the console itself. Joy-Con drift and rail-connection issues are common and usually inexpensive to address compared with buying a new system, especially if the screen and USB-C port are intact.
Repair is typically the best choice when the problem is limited to Joy-Cons, the fan, or the battery, because those components can restore normal play at low cost. Replacement tends to make more sense when the tablet portion has a failing USB-C port, swollen battery, or intermittent charging that suggests board-level issues; those can be costlier and may recur.
Also consider how the system is used: frequent dock/undock cycles stress the port, and heavy travel use increases drop risk. If the console is near the end of its life and needs both port and battery work, replacement can reduce risk.