Arduino MEGA Vs UNO

Here is the basic difference between MEGA and UNO

Screen Shot 2013-04-30 at 12.47.52 AM

So you can see from the table that in UNO you have less data pins, so if your project needs large number of data pins go for mega but dont use MEGA in a small project like Digital Door Lock System. There are also variation in Flash Memory, SRAM and EEPRAM.

IMAG4552

References
http://arduino.cc/en/Main/arduinoBoardUno
http://arduino.cc/en/Main/arduinoBoardMega2560