The title says it all - which camera is better in low light?

I own both, and haven't done extensive testing, but would say they're basically equal. In some situations, the TMC40 might have a slight edge.

Interestingly enough, both of them perform better in low-light than my Canon 7D with anything smaller than an f1.8 lens.

now that's very surprising about the the 7d Dan

everything ive heard actually says the tm700 is actually a tiny bit better in low light than the 40

Technically, with it's f1.5 lens the TM700 should best the HMC40. However, at 1/30 sec shutter, I've found 18db with the TM700 to be unusable where the HMC40 is fairly noise free at 24db. The TM700 has "Color Night Mode" which requires only 1lux light, but any movement and the clip is doomed.

I'd be interested to see if other's mileage varys.