I'm sure I sound like a broken record by this point; but there are roles for both mobiles and computers (be it 1:1 computing as with the OLPC, or 1-computer classrooms, or simply computer labs). Mobiles have high penetration rates (but how young? elementary school?) but limited capabilities beyond 1:1 or expensive 1:many communication. Computers are much more fragile and require more infrastucture, but have such a wealth of educational software and information (especially if you add in the Internet).
Neither are silver bullets to heal a failing education system, but both could play a role in extending education (call-backs to listen in to class for rural youth unable to attend school regularly?) if implemented with a reasonable and maintainable budget and good integration into the existing education processes.