Let's Make Robots!

Help me choosing materials/components for my robot

Hello, i need to make a two wheel self balancing robot , like this one: http://letsmakerobots.com/node/19558 .

I need help about components:

1) about microprocessor i saw Arduino UNO and Ardquino NANO ,nano is more expensive, there is real difference about this two controllers???

2) Gyroscope i have already - ADXRS610Z