XBMC installer versions? Multiple menu options?

forgive me, another n00b as I am new to the ATV and ATV Flash. Everything is exceptional so far and up and running, just tweaking the box to my liking. However, I wonder why there are different installers spread in the ATV menu, e.g. under nito --> maintenance, under XMBC/BOXEE and also under Maintenance itself? Are these different ways to get the same result? Son’t have the menu in front of me now but Nito and Maintenance both show Plugins, e.g. Also, within XBMC/Boxee --> Update there are for XBMC three (3) menu options, from XBMC main installer, then some beta / nightly update and finally the SNR (?) installer. Are these cumulative, i.e. do I have to install them all (in a special order) or shall I pick one (if the latter, which one would be best for me - remember: N00b?).