In my experience small to medium sized tournaments is the easiest way to make money in online micro stakes games. The main reason for this is rake. When you enter a tournament, you pay a fee of typically 10%, and then you get to play for hours without paying anything again. In cash games on the other hand each and every time, you get involved in post flop action, the poker site charge you around 5%.
The result of this is, that while your hourly winrate before rake might actually be fairly similar, the poker site will keep most if not all your profit, if you play cash games. If on the other hand you play tournaments, its pretty easy to get to keep more than half of the money, you actually win from other players, for yourself.
In the past this was less of a problem, because cash game players were really bad, and rake-back deals were also better. If you can make 10 BB / 100 in cash games and then also get 30-40% rakeback, you are making great profit. But today typical winrates are more like 3 BB / 100, and rakeback is almost non existent. So in my opinion cash games have become a bit of a raketrap, and it is much easier to make money in online tournaments.