I don’t know the specifics of the different proposals, but I have heard from industry sources that there is concern with fracking for gas production that potable aquifers might be contaminated by the propant chemicals, etc. during the process. I suspect deep geothermal is deep enough to be below saline brine aquifers, which would not matter if contaminated. That might be the difference. I would assume some gas operations are also deep enough not to endanger any water that might someday be desired for human use, maybe even most of them. The other issue with extraction, such as gas production, is shrinkage of the rock as the pressurized gas is removed, or shifting of the rock after fracking, which results apparently in microseismic events; I believe these are occurring in tight gas fields near Dallas if I recall the news correctly. If the deep geothermal involves circulation insted of extraction, it might not have the same risk of seismic activity. I think the tremors are only on the order of magnitude 2 or 3, so not particularly damaging, but still, earthquakes occurring in areas that have never had them before can be disconcerting, and I suppose there is some possibility of some sort of related sequalea that might be damaging. At the same time, the US has huge supplies of tight gas if we believe the recent estimates, and avoiding the financial and security drain of foreign oil purchases has to be a high national priority.