Arduino uno+ WiFi shield v/s Arduino Yun

I am creating a project in arduino with Wi-Fi capabilities. So I wanted to know the difference between using the above two approach. Or will everything remain the same?

I'd like to know this too. What is the difference between Arduino Yun and Arduino Uno + Wifi Shield? The Arduino Uno + Wifi Shield doesn't look like it can plug into the printer cord like usual?

Maybe that the wifi shield with the arduino costs more?