Both situations are pretty bad, but I still think an accident is more serious. A rolled-back odometer affects price and maintenance, and you can actually check it in a VIN report. I used FAXVIN for that where the site’s easy to use, and the reports are cheap if you buy them in bulk. But a hidden accident might not be visible at all. That’s when you really need a good mechanic, a full inspection, and all that. If the car was repaired poorly, you could be taking a real risk while driving.