I think they are both very promising projects. I have invested in GNT, and I will also invested in SONM.
they have both a potential, although sonm it slightly very slow to reach its ico price now, still i think it takes time, it will definitely reach its price sooner or later just wait for it. invest what you are afford to lose.
Yes they are both good looking project but I invest in Sonm though the price is cheap now in the exchange. I think sonm price will increase in the exchange as this project is new.