How do evacuated tubes and flat solar panels differ in performance?

In terms of solar energy collected per collector area, evacuated tubes have higher efficiency.  Nevertheless, per solar panel area, flat panels have larger collector area, and will perform better in the Philippine climate.

Evacuated tubes are designed to collect solar energy at higher efficiencies within a wider range of angles with regards to the sun's position.  Evacuated tubes can reach higher temperature than flat panels.  They are best suited in climates when total solarization per day is not high.

Flat panels can collect the most energy when they are perpendicular to the sun's rays.  Thus, flat panel performance is affected more by the angle with respect to the sun.

Physically, however, per panel area, flat collector area will be larger than evacuated tube collector area.  In effect, the lower efficiency of the flat collector is balanced with its larger collector area.