Beta is the release that occurs once by month, snapshots are release made in between and are then more advanced than the beta that came before them (as they're build on the current state of the code).
Meaning they have more bugs fixed in comparison to the beta , but when something new or a code refactor is done may have some new bugs.
But it's always worth it to get snapshots as many of the beta bugs are fixed and you can help the devs by reporting the "new" bugs.
You can find snapshots here :
viewtopic.php?f=26&t=15733at the time i wrote the krazyweb link has only old snapshots, so use the cardforge one , the latest snapshot (for window) at the time is :
forge-gui-desktop-1.5.30-20141109.015032-5.tar.bz2
on that page :
http://cardforge.org/releases/snapshots ... -SNAPSHOT/