headers_out vs err_headers_out with temporary redirect 302

Hello, 

From the doc:
===
The difference between headers_out and err_headers_out, is that the latter are 
printed even on error, and persist across internal redirects (so the headers 
printed for ErrorDocument handlers will have them).
===

It's still unclear to me what to use for temporary 302 redirects, headers_out 
or err_headers_out? I tried headers_out and it works. But probably I am 
somewhere wrong?
--
Anton Petrusevich