@LittleBrandyLove These aren't stupid questions at all; plenty of people have been using discs for TS3 and don't know where to start with Origin. Besides, it's much better to figure this out before you spend your money.
The biggest reason to buy disc copies instead of digital is that your install wouldn't be tied to Origin. You could play offline, without signing in, you wouldn't have to deal with the pack selector, and you could skip the launcher entirely if you wanted. (Google "sims 3 patch 1.69" if you're curious about the issues.) This is all dependent on your owning a base game disc manufactured before September 2012, but if you don't have to play through Origin now, that wouldn't change when you installed another disc. (Just make sure not to let the EA Download Manager control the install process, or it will do everything it can to "upgrade" itself to Origin, patch your install to 1.69, and take control of your game.)
But if you install even one pack through Origin, your game gets automatically patched to 1.69, and all the consequences of an Origin install follow. So if you're buying anything from Origin, you might as well buy everything through the app. Also, if you already need to launch the game through Origin, it's probably better to just buy and install digitally.
Of course, disc copies of TS3 packs are hard to find. Places like Walmart and Target still have some inventory, but there's no guarantee that you'd find the packs you want.
The other alternative is Steam. It sells every pack except Katy Perry, and your patch level on a Steam install would be 1.67, so you'd avoid Origin entirely. You would have to buy the base game from Steam as well, but during occasional sales (a few times a year), the base game and packs are priced as low as $5 each. If you ever changed your mind and wanted to go the Origin route, you could take the CD keys that Steam provides with your purchases and register them in Origin, and your content would be added to your game library just like it is when you register a disc.
