How much CAD do you need? Most people don't need anything more than the free version of OnShape, which is quite nice.
The need-based argument is somewhat of a narrow view. Say your workflow involves taking in dumb solids (parasolids, STEP, whatever) and doing something with them. Maybe modifying them, or maybe making fixtures. Can you work with those in Solidworks? Sure. Can you work with them in NX? Yep. So you don't "need" NX since Solidworks does the same thing. Only the difference is that Solidworks feature-set for that kind of work is hilariously limited, whereas with NX + synchronous modeling you'll pretty much never miss the feature tree again.
What kind of thing do you want to do, how much do you have to spend, how much do you value tools that work well instead of just technically work, etc. If you're completely new to CAD, then get Fusion360 or OnShape and learn how to use them. Then you'll be in a much better position to determine what you do/don't care about when you're ready to spend money.