32g will give you more in the 1.8-2.2Ω range than 30g will* unless you go with more wraps on the 30g, which will take longer to heat up. but the thicker wires are easier to wrap then the higher gauge wires.
*this is with 4-6 wraps on a 2.5mm diameter wick. however ive got gennys set up with 32 that are 1.2 and 1.3Ω. this is with 3 wraps. so, it really just depends on how many wraps you use.
also, if you want to decrease the resistance of your wire, you can run two equal-length strands parallel to each other to create the effect of thicker wire. or you can twist two strands to the same effect.