Old Town
Old Town is the Royal Mile and the streets running off it — cobbled, steep, and packed with the biggest Fringe venues (Pleasance, Underbelly Cowgate, Just the Tonic, Assembly Roxy). Festival prices are aggressive: a flat that lets for £900/month in winter will list at £3,000 or more for August. Crowds are constant. The energy is what you came for. If your show or your tickets are in Old Town, the convenience is worth the cost.