Ok, just some opinions on when is the best time to tumble brass.

Before of after resizing & decapping? And why?

Never ;-)

I tumble before I start the reloading process on all calibers takes the scratches out before I I run them through the dies.
I do this especially for auto rounds

When I get home from the range I threw my brass in the tumbler.

If you tumble your brass after you resize and prime it you can have issues with misfires. The media can get stuck in the primers and prevent ignition of the powder. So, I just do it before I start any part of the reloading process.

when ever the mood hits but always the spent primer in. what a pain getting the media out of the primer pocket.

That's why I asked. I was doing it after resizing thinking it would help with cleaning the pockets. I spent alot of time cleaning out the media! Thanks for the help guys!

I do it before resizing and decapping for the simple reason of picking media out of your primer pockets. Another reason is you have clean brass to inspect for any damage before reloading.

I do before resizing.

X 2

I do it before sizing to keep grit from scratching the dies and, if I have to lube the cases (no carbide die), I then tumble again to clean the lube off before I prime. Lyman makes a pick just for getting media out of primer pockets.

Lee has a special de-capping die I use first, then I tumble. It seems to clean the pockets a bit. I use a straightened paper clip to dislodge the media and I do that when I'm inspecting the brass. Sounds lame, but I've been doing it for years.