Should I stay in Colombo or head to Galle?
Most itineraries treat Colombo as a short stop and Galle (or a nearby beach town) as the real south coast base for a longer stay.

Sri Lanka's capital city compared with the south coast fort city — for travelers deciding which deserves more of their time.

South coast fort city with Galle Fort, lighthouse viewpoints, Dutch colonial streets, and nearby beaches.
Sri Lanka's capital city, with temples, museums, markets, Galle Face, and the Lotus Tower.

Galle — colonial streets, a lighthouse, and beach towns nearby make it worth a full day or more.
Colombo — most visitors treat it as a one-day stop rather than a multi-day base.
Galle has real beach towns (Unawatuna, Mirissa) within a short drive. Colombo does not.
Colombo is usually a first or last stop near the airport; Galle is usually a dedicated south coast base.
Most itineraries treat Colombo as a short stop and Galle (or a nearby beach town) as the real south coast base for a longer stay.
For most travelers, yes — Galle Fort and its nearby beaches offer more to do across a longer stay than Colombo's city sights.