What's the difference between CAA license and FAA license and which is better?

to make it more clear he FAA is better coz its more accurate and recognized 

the difference is FAA in USA CAA in UK

CAA stands for British Civil Aviation Authority and no longer used after the merge with European Aviation EASA (European Aviation Safety Agency) so this is the new equivalent EASA License to FAA (Federal Aviation Administration).

Both have two way acceptances to be recognized.

If you are FAA you can convert to EASA and vise versa, depending on the place you work under its regulations (some countries work with FAA and some work with EASA).

If you fall under FAA and need to certify an Airplane regulated with EASA you need to have the conversion to EASA to certify it. And vise versa.

This is in brief.

Good luck.

FAA - Federal Aviation Authority (USA), CAA - Civil Aviation Authority (UK). Nothing to choose between the two but the FAA is more "recognisable" in the aviation world.