Traktor is for the creative mix DJ. Native Instruments is your go to choice if you want to remix live or in the studio.
VDJ is for mobiles. It's a rubber meets the road player that will let you mix with whatever controller you prefer and include video as well. Like Serato (which is better if you own a MAC) it resolves audio and video to be self contained on a personal PC making it easy for DJs or nearly anyone to use it and start playing.
VDJ is better for all around use (PCDJ as well, but not as widely used). Traktor is, as Bob said, for creators, good FX, built-in scratch. It goes on sale at least once a year (usually around Black Friday) for $50. This upgrade only worth it if you already have Traktor Pro 2 (I do) and want the current version.
I own Serato DJ, Traktor 2 and PCDJ DEX RE .. I'm looking for an app that has great search capability, automixing (as necessary), video and karaoke. I don't care too much about remixing tools, beat tools, or scratching support. Algoriddim looked good, but the Windows version is inferior to the Mac version and I have more Windows PCs and it doesn't do video on a PC and no karaoke on either platform. Serato/Traktor don't do karaoke (yes I could probably use another app for the few times but I would prefer consistency). Mixxx doesn't do video or karaoke, so that one's out.
PCDJ DEX does all 3 and VDJ does all 3. My DEX RE (Red Edition) does basic karaoke but no video .. the upgrade cost to full is $119. VDJ is steep at $299, but is the god standard for mobile DJs, though Serato wins for most club jocks.
That was going to be OtsAV but, they went MIA on their product development, bet against Micrsoft (and lost.). Lots of big ideas - no follow through.
There are better solutions for video than DJ software, so that's why I'm favoring Mixxx for mobile DJs. It's open source with no licensing bullsh* and regular continuous development. You do have to either write your own midi scripts for controllers, or find someone who's done one for your model and shared it.
The young are all about the gadgets which makes Traktor and Serato so popular. Both brands will keep you amused until you run out of money for new gear.
I like Siglos Karaoke Pro as a separate karaoke player. It's simple enough that you can actually show someone how to use it in less than 5 minutes and then leave them to run their own show. Great for DIY and rental. Hosting I've been able to run it concurrently with a DJ software giving me access to both sources. Not bad for $99.