is more efficient (it runs cmd as few times as possible, unlike exec, which runs cmd once for each match). However, you will run into trouble if filenames contain spaces or funky characters.
The following is suggested to be used:
find . -print0 | xargs -0 cmd
this will work even if filenames contain funky characters (-print0 makes find print NUL-terminated matches, -0 makes xargs expect this format.)
The first version is shorter and easier to write as you can ignore 1, but
the second version is more portable and safe, as "-exec cmd {} +" is a relatively new option in GNU findutils (since 2005, lots of running systems will not have it yet) and it was buggy recently. Also lots of people do not know this "-exec cmd {} +", as you can see from other answers.