Bio-fuels are theory, nuclear power is fact. I was a big proponent of bio-fuels until I realized two things.
First, the resources required to create bio-fuels is enormous. Bio-fuels is a means to store solar power into chemical bonds, the biological processes are an intermediary. As an aside there are other means to store solar power in chemical bonds that does not involve biological processes but they suffer many of the same downfalls. Just the land required alone for bio-fuels is problematic. Sure, we can put the collectors on roofs and perhaps even in the roadways but that only adds to the complexity and cost. There are also limits on where these things can be placed, there must be enough sun and temperature extremes means more cost and complexity. Nuclear and fossil power on the other hand is relative compact, can be placed just about anywhere (even on ships at sea), and can tolerate all kinds of weather.
Second, bio-fuels will always compete with food for resources. Whatever it takes to grow algae, sugar beets, switch grasses, or whatever the favored bio-fuel of the day is takes the same land, water, fertilizers, etc. that food does. People need to eat and people need heat and light, bio-fuels will always have the potential to force people to choose between the two. I will admit that non-food plant life does not need to meet the same rigors of sanitation and such that plants for food does. The problem still remains that any area on this earth suitable for growing bio-fuels will also be suitable for growing food.
Wind and solar power share many of the same problems that bio-fuels do in land, sun, weather, and so on. Humans have only been able to rise above subsistence living once we've moved beyond wind, solar, and bio-fuels. I fear that even with the most advance technology we can dream up cannot over come some real limitations to wind, solar, and bio-fuels. With the promise that nuclear power holds I believe there really is no other choice, we cannot maintain our standard of living unless we move to nuclear power.