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Both are fairly easy, Frogbit has bigger leaves and roots hanging down, Duckweed is a better nutrient absorber while not having noticeable roots , Duckweed is more adaptable to water conditions than Frogbit, Frogbit is nicer to look at ( imo), both need consistent population control but Duckweed grows faster so more work.
I have Frogbit in my tank and it grows great
In fact, occasionally I have to remove some of it so some of the tank's top direct light gets to the other plants.