I don't have a ton of experience at all levels, but generally speaking, I think that the majority of a poker player's money come from fish. The lower the stakes, the more players, and thus the more fish. Also the lower the stakes, the better the likelihood of coming across inexperienced players because most good players will eventually grind it out, succeed, and move up. And lastly, I think the lower the stakes, the more likely a player is to play for recreational purposes, not care as much about losing or tilting or being reckless and the like. These are just generalities - there are always some sharks and fish at every level, but I do think there is a correlation between the stakes and the distribution of sharks and fish.