I have a Green gas HFC G17 Blow back. Its handled fairly well, granted I haven't shot it much during the winter. One of my team mates had a green gas and as most know it doesn't like the cold much, got to the point of holding the mag in his hand to keep the gas warm till he would take a shot then pull it out and hold it again.
As for Green Gas vs. CO2. my only other pistol is a CO2 glock. 'fraid I don't know the make. Some off brand I bought years ago at Dunhams sports. The CO2 definitely shoot harder then the green gas. It is a non blow back. As far as weather has been concerned, I have had little to no issues with temp.
Agreed though, blow back does look cooler even though it expends a bit more gas for the blow back function. If you worried then about gas getting expensive, CO2 is cheap. Least, I think it is... Green gas tends to be a bit more expensive. So your options there are, eat the price and buy the gas, or buy an adapter and go to propane. Just make sure your vigilant about adding oil to your gun as that is what green gas is, propane/oil mix.