Vinyl or CD?
It depends what you want to do and achieve.
If you just want to be a DJ (i.e. play music to people in clubs and parties etc, you’ve got a wealth of options. For example, you could use: turntables (to mix vinyl records), CDJs (to mix CDs), DJ software like Virtual DJ (to mix digital tracks via a laptop), a midi controller combined with software such as Traktor (to mix digital tracks) or turntables combined with a digital vinyl system (DVS) such as Serato (to mix digital tracks using time-coded vinyl). You can even use a combination of all of these!
If you’re intrigued by turntablism and the desire to scratch, beat juggle, battle etc, I’d always favour turntables and vinyl over other setups. It’s the authentic and true expression of the artform. It is possible to scratch with CDJs and midi controllers nowadays but it isn’t quite the same feel because turntablism is an analogue artform (a needle moving along grooves in a piece of vinyl) which means it doesn’t always translate too well digitally.
I guess you have to weigh up the pros and cons. MP3s and CDs are easier to acquire (and most of the time cheaper) than vinyl but there’s things certain things that are only possible with vinyl. I think it’s a case of choosing the right tools for your needs, tastes, and goals, then it’s in your hands to master those tools.