Palestinians are quite obsessed with Felafel - understandably so: it is delicious, filling, widely available and cheap. And it can be eaten for breakfast, lunch, dinner or as a snack. Everyone seems to have their own favourite felafel shop in town, so I wonder if branding and habit is the main indicator of a good felafel, rather than taste, quality, price etc.
Unfortunately the first article I found when searching google for "how to evaluate felafel" was a research paper that evaluated the effect of feeding felafel to rats for 30 days... which made me evaluate my research process and invite a number of friends to participate rather than doing the research myself.
What I did learn from the article was that the frying oil is key to the health (and presumably also the taste) of a felafel. Older oil (more than 3-5 days) is not as effective in frying and requires a longer cooking time, in which case the felafel can absorb up to 25% more oil. My guidebook similarly warns of darker looking frying pans in the snack bars, but I find it impossible to evaluate whether the oil is too dark, given that the frying pans are made of black metal!