There are also 2 types of penis, not sure what they’re called in English exactly but we call them blood penis or flesh penis. Blood penis is quite small unerect but can grow up to multiple times its size and also gets thicker when erected. The majority of men actually have this type of penis. The other type is the flesh penis, which is almost the same size whether erect or not. It doesn’t grow much when erect. Both of course get hard when erect. Since I sometimes see those jokes about small penises in unerect state I assume that quite a few people don’t know of these 2 types and their differences, and if you don’t know this kind of important detail then a flesh penis might look more promising when you’ve only seen it unerect. But, of course, there can still be size differences between different ones. Independent of the type. Anyway, the main point is if you really want to compare penis sizes you always have to do it in erect state, otherwise it’s completely meaningless.