PC for the Poor: Which design will win?

It's easy to list the benefits of bringing inexpensive computers to the billions of people who live in rural villages and urban centers in the developing world.
Designing machines that are resilient, powerful and cheap enough to reach those not yet online, though, has proven a lot tougher than expected. India's Simputer, an inexpensive handheld, flopped. Brazil has worked for years on a Linux PC for the poor, to no avail.
Recently, some new ideas have come to the forefront. Here's a quick rundown of their pros and cons.