If your opponent is more apt to 3bet you than to flat your raise, then you want to risk as little as possible to steal his blind (I consider 2.01bb to be essentially the same thing). At higher stakes especially, people are much more aggressive preflop, so if you're raising larger amounts then you're giving up more fold equity on a frequent basis when you're forced to fold to an opponents 3bet. And by not raising a larger amount you can safely fold with more frequency than if you were raising with 2.5bb for example. And if you can fold with more frequency, then you can steal blinds with more frequency.
At lower stakes opponents tend to call with more frequency rather than 3bet. In this case, you may want to raise a larger amount, such as 2.25bb or 2.5bb, because you're not very concerned with being 3bet as much. This is especially the case when you have stronger holdings and there are passive fish in the blinds, you can even raise 3bb effectively to get maximum value and steal efficiency.