[Kurn, son of Mogh]

First, understand what variance is. Variance is defined as the standard deviation from your win rate.

Winning players in NL build their win rate by taking advantage of bigger errors by their opponents and not making as many big errors themselves

Winning players in limit build their win rate because the marginal value of their opponents' small errors sum up to a greater number than the marginal losses when those opponents suck out.

The bottom line is that in the latter case, a similar win rate will naturally have a higher SD than in the NL example.

Thus limit has a greater variance than no limit.

Note: Bad players losing money faster at NL is NOT an example of variance. Variance is simply a measure of the fluctuations one can expect when playing optimal poker.