I have a lot Mi3 and tried the G2, and I have to say that both are amazing, the undisputed kings in quality / price. For the two specifications are matched and do not missing anything, but keep in mind that the Mi3 not have 4G support in Europe (I do not consider it necessary for me but some people do not want to sacrifice this). The mi3 is around 240-250 €, although Spain with direct shipping (1-2 days) I went to my 270 €. Of course, with warranty and SAT in the store.
The G2 is slightly more expensive but has the 4G and a tad more screen, plus a very well exploited size (Mi3 is perhaps a little big in this sense), but only has virtual buttons. In everything else is equal, I stayed the Mi3 but certainly the G2 has always seemed the best option within the continent.