The tables / spreadsheet functionality can be super helpful when you just need to jot down thoughts which lead to comparisons which lead to calculations which lead to helping you decide which path you want to go down. It's really great to not have to leave the context of what I'm doing and just open up an org mode buffer and jot down my thoughts and then come out with an answer that is backed by calculations I'm confident in. Very handy 'back of the envelope' or 'napkin' alternative!
For anyone looking for a good place to start, here's a great resource: http://doc.norang.ca/org-mode.html#GettingStarted