Which is better for my case, Arduino UNO or Arduino Leonardo ?
A 'no brainer'; The Leonardo is a significant upgrade from the Uno, including more pins. Here's the kicker: it costs less. Better for less, how often does that happen? Now that I think of it, perhaps, in the world of electronics, that might not be such a rare occurrence.
I can remove the ATmega chip and use it in a PCB ?
If you get the Uno and the ATMega MC is ia DIP(dual inline package), yes you can. If the Uno you get has the ATMega MC as a SMD(surface mounted device, you can't just pop it out and put it into another board. It could be removed and solderred into another board but it would be tricky and difficult and I think, pointless.
- Scotty