Among mainstream or green media, you can find a lot to support the opinion that urban life is the green choice. There are undoubtedly some significant energy savings when you live in a multiple-family housing environment, and particularly if you can ditch the car.
If we're going to compare the typical rural family with the typical urban family of today, I think these stories are spot-on. The picture changes significantly when we look at what's *possible* in both environments, however. If we incorporate a forecast of future energy scenarios, the urban option takes on significant new shortcomings.
First of all, let's look back into history a bit. If we venture back before the time of the fossil-fueled industrial revolution, we'll find cities that would hardly qualify as such by today's standards. Why? Because any concentration of people requires that all resources (food, fuel, construction materials, etc) be brought in from outside the city. There are numerous instances throughout history of cities collapsing when the distance to their nearest fuel sources (firewood, typically) became too great.
When your transportation options are limited to your own two feet, animal power, or water transport, the area from which you can draw these resources shrinks dramatically -- probably no more than 10 miles for anything moved in significant quantity (though water transport would allow a greater range for high-value items that justify the additional expense). If you're limited to drawing all of your goods from within a 10 mile radius, you'll find that supporting a large city, say of 100,000 or more, is nearly impossible.
Why is this important to consider today? Our fossil fuel sources have now entered a decline which will be exponential in nature. Like it or not, our history, in terms of energy supply, is going into reverse. The ever-optimistic oil industry, in their attempt to retain investors, trumpets the fact that we still have a 54 year supply of oil, though their calculations do not incorporate what is likely to happen to us economically as the price of this energy rises ever higher, nor the fact that our planet would no longer be habitable if we burned it all. The fact that our Federal Reserve now has to inject $85 billion each month into our economy just to keep it on life support should tell us something of where our economy now sits, 6 years after hitting peak oil. That 54 year supply is fully dependent upon our ability to pay for it. Like the cities of old, we're watching our energy supply retreat over the horizon.
Our ability to pay for energy depends upon our economic condition, which in turn depends upon both our environment (climate change, anyone?) as well as the price of energy. Also worthy of note is that the energy return on our oil supply here in the US has dropped from 100:1 to less than 10:1 in 80 years, with most of our newer sources even below 5:1. Chart that trend out for a few more years and tell me where it leads us. Suffice to say that there will always be loads of fossil fuels in the ground that are not worth digging up.
While urban living does offer significant efficiency advantages over rural living, it has an achilles heel which will become painfully apparent over the next decade, and which cannot be overcome. The problem is that urban energy requirements on the modern scale can only be met with fossil fuel sources, no matter how efficient their use is. There is no way for Los Angeles or New York residents to return to burning firewood. The supply simply isn't available within economically transportable distance, and resulting air quality would make China's current problems look like a walk in the park. Any attempted return to animal-based transportation in our oversized urban regions would fail for similar reasons.
So what about the renewable energy revolution and the high-tech green future? Well... It may have some limited application in our future, but suffice to say that much of it is hogwash when you look at net energy return. The solar industry, when all inputs are considered, uses far more energy than actual solar output. Wind may be somewhat better, but I'd be willing to bet that most of it will disappear along with our fossil fuel sources as well. At best, most of what's been presented to us as alternative energy is little more than the leveraged use of fossil fuels.
It is quite possible for a rural family to beat their urban counterparts in energy use. The major difference in current energy use in urban vs. rural areas is that for transportation. There are tens of thousands of rural Amish and Mennonite families who do not use fossil fuels for their family transportation, but rather the "antiquated" horse and buggy, with many of them also making great use of bikes. It always makes me smile when I see an Amish grandpa riding his bike to town, at an age when a lot of "English" Americans (as the Amish refer to the rest of us) can barely fit behind the wheel of the SUV they purchased to accommodate their super-sized physiques.
Keep in mind also that roads themselves require significant energy to maintain (which will soon be lacking). The Amish of the 1800's rarely owned buggies, for the simple reason that most rural areas did not have suitable roads for them. This is one area where downsized urban regions may maintain an edge, as paved roads were historically found only in towns.
The second energy advantage for urban residents is that of heating, though it's realized primarily through the use of multiple family dwellings. The prudent rural resident wins here as well -- by heating with locally sourced wood. Because wood is not a fossil fuel, the carbon emissions to not result in a net gain in biospheric carbon. Keep your population density within traditional standards, and the smoke really isn't a problem either, particularly with newer recirculating stove designs.
Last but not least, it's important to remember that most energy use is industrial, not personal. It's not the gasoline burned in the car you shouldn't drive, but the coal that was used to smelt the steel. It's not the natural gas used to heat your apartment, but the coal burned to create the concrete it's constructed with, and the diesel used to transport the building materials. The rural resident has a distinct advantage here as well, as they have the option to provide for their own food, clothing, construction materials or household goods sourced from local materials, all of which can be (and was historically) accomplished sans fossil fuels.
So while the typical rural resident of today is in fact less green than their urban counterpart, a rural location offers far greater flexibility -- which can, should, and will be used as a matter of necessity. Probably the greatest shortcoming of rural life at this point in time is that of employment (which I should note, is also a product of the industrial revolution).