If you are mainly playing for fun, then I can certainly see the motive from just taking the easy low variance money at 2NL, and you pay less rake as well. My own experience at PokerStars have been somewhat odd in the sense, that I actually have almost the same winrate at 16NL as I do at 2NL, but for 5NL and 10NL its been much much lower.
Some of this is maybe just variance, but it is also my impression, that the 16NL games somehow tend to attract a higher percentage of bad players. Maybe because the limit is overlooked by some regulars, and because its the highest limit, which pop up, if you filter the lobby to show only micro stakes. So those players, who lost most of their deposit and are looking for a quick dubble or bust, might end up at 16NL more frequently than at 5NL or 10NL.
But obviously you need to be able to mentally cope with much bigger swings to your bankroll, since losing sessions of 50$ or more will be completely normal and not possible to avoid. I will also say, that the difference between 2NL and 5NL is much more significant than the difference between 5NL and 10NL.
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