@Dawneyork Each game has its features and drawbacks; the right one for you comes down to personal preference. For me, TS3 is the obvious choice and has everything I want in a sims game, but some people never took to it and have much more fun with TS4.
There are two huge benefits to playing TS3 over TS4. The first is that TS3 has a completely open world—your sims can go anywhere in town while you follow their progress, and you can switch back and forth among them with one click. TS4 only allows one lot to be active at a time; even going to your next door neighbor's house requires a loading screen.
The other major advantage of TS3 is that it has a color wheel and hundreds of patterns that you can apply to any object or article of clothing. You can recolor sims' hair and eyes as well, in whatever way you want. TS4 only offers a few preset patterns to choose from. So if you're into styling your sims in your own patterns, you'd be stuck downloading piles of custom content just to get the same flexibility.
(It's also a benefit that TS3 is finished, with all of its content already available. What patches there are have been released, and the bugs and their fixes described in detail.)
The biggest feature of TS4 is the increase in options for shaping sims' faces and bodies. Many players never became comfortable with TS3's sliders, but even putting that aside, TS4 offers a variety of extra shaping tools that its predecessor doesn't have. From all reports, TS4's tools are also easier to use.
The other major consideration is that TS4 runs better on lower-end systems than TS3 does. The demands of TS3 aren't excessive by current standards, but this game can be unforgiving on hardware that's not up to the task. TS4 can run on specs that wouldn't support TS3, although the newer game isn't finished, and its requirements may eventually match or exceed those of TS3.
If you want to get a better sense of what it's like to play the two games, you might want to watch some youtube videos. Carl's sims guides are also great resources.
https://www.carls-sims-3-guide.com/
http://www.carls-sims-4-guide.com/
If you'd like to know whether your computer could run TS3 well, you could post your specs here, or a dxdiag if you don't know how to find them. To run the game and all its packs on high graphics settings, you'd need at least a 2.4 GHz processor (not U- or Y-series), a dedicated graphics card at least as strong as an Nvidia 960 or 1050 ti, and 6 GB RAM. (Despite rumors to the contrary, the game runs just fine on Windows 10.) Here's how to run a dxdiag:
https://answers.ea.com/t5/The-Sims-3/HOW-TO-DxDiag-PC-Only/m-p/1049584/thread-id/47181
