How much hard drive space do you have?
HV20 is HDV, so like 13 gigs an hour of source footage. the HG10 is AVCHD, and FCP/FCE/iMovie convert it to ProRes422 (but imovie is only AIC). And that comes in at like a bit less than a gig a minute. Pick your poison.
They're both GOP based formats, 4:2:0 chroma subsampling, HDV has a higher bit rate, but h.264 is a totally different format with better compression than hdv.
I'd say go with the HF100 or hf10. Full raster 1080. AVCHD based. Do it...