When the complete 2.1.0 comes out, would it be possible to upgrade the beta's? or would i have to reinstall the boards? because i am thinking whether i should install 2.0.4 or 2.1.0

any ideas?

When 2.1.0 Final hits then yes you will be able to upgrade the Beta's to the Final release or you could submit a ticket and IPS could do it for you...

is it possible that if 2.1 doesnt work out so well and i deupgrade it to 2.0.4?

lol. i know i sound like an idiot, but i need to know

According to this post there isn't a way to downgrade from 2.1 to 2.0.4 and a downgrade path will not be provided either so it's up to you of which version you want to use...