Neither of those are passing variables, those are setting environment variables. Bash (probably most shells?) mixes its variables with environment variables, and "export" is how you promote a bash variable to an environment variable. The inline version (GGP's [THE=tell the] version) sets the environment variable only for that one executable, while an exported one persists.

Also I'm guessing you didn't test that, you got the quoting wrong (it prints nothing, the second one should be single quotes) ;)