99600c1d_Collector___Solar_Water_Heater__Evacuated_Tube_Collector
[S.No] 10 [Flat Plate Collector] The collector fins & tubes being flat the incident sun's rays will be at 90 degrees at noon only for peak absorption [Evacuated Tube Collector] 
The collector glass tube absorbers being cylindrical the incident sun's rays on the tubes is at 90 degrees throughout the day. Hence peak heat absorption always.
Comparison between Evacuated Tube Collector & Flat Plate Collector - Solar Water Heater
Evacuated Tube Collector