I cannot give you pro advise on traktor as I have been evaluating which route I will go.
However I have played several gigs on a borrowed S4 of course using traktor and have been playing around with VDJ on a buddies ddj-ergo (yeah he is a bedroom DJ, but I just wanted to test-drive VDJ not really into the Ergo).
I have to say after a few weeks: Traktor get’s the job done, the S4 is OK, but IMHO very overpriced and the sound quality especially of the effects is excellent. But you pay with some lacking things, that some “Pro’s” might consider obsolete (you dare to use sync???) and that Traktor to me at least was not very intuitive and customizing it is a royal pain.
Playing with VDJ I have to say this software is hugely underrated and probably has a bad rep from older version (no idea). It worked well for me and at least through my monitors it sounds excellent and not unlike traktor. However some of the built in effects and the EQ are rather sad. However I found VDJ extremely intuitive and easy to customize, skins, VSTs etc. etc. etc. all really easy.
Now the software I liked most for sound, precision and effects was Itch, however I really dislike the Twitch I had for testing and I really do not find any Itch controller very appealing. I wish Serato would allow us to buy Itch for a controller of our choosing….