To each his own, but I have all maps. It's not a bad idea to buy them all, if you can afford it. As far as Origins goes, I like it.
I think alotta people say NAY to Origins because if you do follw the storyline it WILL upset you in the end. Now if your looking for just a new map to kill Z's in, then YES.. Origins isn't a bad map at all. Now if you want my Honest opinion.. Buy Resurrection on BO1. This will give you more for your money. You get all maps from World at War.. Nacht der Untoten, Verruckt, Der Riese, and Shi no numa. Plus you get Moon and a pretty awesome soundtrack with all songs from each map.
So Ressurection is definitly worth the $15.00
Nothing wrong with origins, it is second on my list for BO2 zombie maps, i see it as a solo map cause without teamwork you will not be going anywhere fast or far and there is just a bit too much to it. BO maps are grate and they are very simple, kill zombies to make points and move on then save a crawler for a toilet brake you seriously can play without a mic in a team and get far, origins on the other hand will go something like this... save last zombie in every round so we can kill zombies over here and then over there and babysit the zombie a bit longer so we can get this harry potter sticks ouuu dont get me started on these stupid knuckles.
If you like solo games then get origins as realistically you will probably end up playing this alone if you want to hit some long games, but if you like team games BO maps is the way to go.
Hope you enjoy whatever you pick, main thing have fun!