BasicMed carries operating limitations written into FAR 61.113(i). You may not fly above 18,000 feet MSL, you may not exceed 250 knots, and you may not fly outside the United States unless the country you are entering has authorized it — which most have not. You are limited to private pilot privileges, meaning nothing for compensation or hire, and BasicMed can never be used to exercise commercial or airline transport pilot privileges.
There is also an aircraft limit. As BasicMed was originally written that was 6,000 pounds maximum certificated takeoff weight and six occupants. The FAA Reauthorization Act of 2024 raised those thresholds substantially, to 12,500 pounds and seven occupants, which brought a large slice of the piston twin and light turboprop fleet inside the rule. If you are buying an airplane on the strength of that, confirm the current figures against the FAA's own BasicMed guidance rather than a forum post.
So: who should stay on a third-class medical? Anyone who might fly for money, anyone heading toward a commercial certificate or an instructor rating, anyone who flies to Mexico or the Bahamas regularly, and every student pilot who has not yet held one. Who should move to BasicMed? A settled private pilot over 40 who is tired of a two-year FAA cycle, and particularly anyone carrying a stable managed condition whose special issuance paperwork has become an annual chore.