its depend on what would be your purspose/intention of using those camera.

if you are into point and shoot  alike camera, light weight, street photography, unique look. that would be the Sony NEX 5 or NEX 3, 

if you are into going deeper in photography and willing to invest more variety of lense, Amature to Serious Photography, full manual control? Canon 550D will be a very good start.

Note: both camera are great, and camera equipment are just a tool, it is always the photographer's skill really matters.