You can look up ratings at the
Florida Solar Energy Center. The Magen Plastic Medallion MD-30, MD-40, and MD-50 are unglazed flat plate panels (basically plastic tubes) with 83.7% efficiency and a 3.250 (and 4.959) efficiency loss from temperature difference (in IP units). The Techno Solis C20ts20-2, C20ts16, C20ts15, C20ts14, C15ts16, C15ts15, C15ts14, C15ts12, C15ts10, C15ts08, C20ts12, C20ts08C20ts10 for most are 82.2% efficiency and a 2.880 (and 1.053) efficiency loss from temperature difference. The most efficient panels of this type are Fafco Revolution have 86.2% efficiency with a 2.608 efficiency loss from temperature difference. The Techno Solis TS-40, TS-32 are glazed flat plate with 70.4% efficiency but only a 0.610 (and 1.570) efficiency loss from temperature difference.
So if comparing the unglazed flat plate panels, then the Magen Plastic Medallion are a little more efficient but not by much. If you are looking at the glazed TS-40 or TS-32, then that is completely different. While glazed panels are less efficient when there is no wind and no temperature difference between the water and the air, they don't lose efficiency very much from wind nor from a larger temperature difference. Usually glazed panels are used for domestic hot water heating, but they can be used for pools if you tend to keep your pool water warmer than the air temperature or you are in an area with a lot of wind and at least some temperature difference between water and air (with air cooler than the water). See the thread
Solar Panel Technology Comparisons for more details about different types of panels.