This depends on the way you are looking at it and what you actually want. As far as am concerned, the two could be very rewarding if adequately managed. In comparism, water management in earthen pond is easier than in concrete pond because most wastes from the fish and the feeds are absorbed by the soil n earthen ponds while they have to be flushed out in concrete ponds.
Also phytoplanktons and zooplanktons are available as additional sources of feed in earthen pond while artificial feeds are the only source in concrete ponds. There is no need to clean earthen ponds as it is done for concrete pond. However, it is easier to ensure adequate security with concrete pond than with earthen ponds because most concrete ponds are usually built in and enclosure. Also sorting, numbering and harvesting are easily done in concrete ponds than in earthen ponds.
Diseases, cannibalism and death is also easily observed in concrete tanks, meanwhile how well the fishes are consuming and absorbing their feeds is easily known in concrete ponds than in earthen ponds and more importantly, you do not need a water-logged (swampy) area before embarking in concrete pond construction.