How George III would cross the Atlantic

If George III visited the American colonies, would he travel in a royal yacht or a warship?

Probably a suitably fast third rate with a large escort, because contemporary royal yachts were not designed for transatlantic voyages.

Royal yachts of the period were intended for shorter royal movements and ceremonial use rather than an Atlantic crossing. A third rate offered better seakeeping, speed, accommodation, and military strength. The chosen warship would temporarily become the royal transport. A substantial escort squadron would surround it because protecting the monarch would outweigh ordinary cruising economy.