A cash or investor buyer removes financing risk and an appraisal condition, which is real value if your timeline is measured in days rather than weeks. What it does not remove is the fact that their offer is built to leave room for their own resale profit, so the number starts lower before any negotiation begins.
A financed buyer working with a lawyer through the usual Information Services Corporation title process is typically only 2 to 4 weeks behind a cash close once an offer is accepted, which is a small time cost against a much larger price difference in most cases.
Run the actual numbers on your specific house before deciding, because the certainty is only worth paying for if the gap in price is genuinely justified by your timeline. Get your hand-reviewed valuation from Joel Dyck.