I totally agree, there is not a real BETTER here.
Currently it is simply the amount of features and the quality of some of the features (F/X for example) that make Serato the winner by points.
However if you do not need any of those features or even prefer a more simple setup, or the way the iTunes integration works in Djay then it might be for you.
I have tested Djay Pro extensively since the introduced the parallel waveforms and even played some small gigs (if you can say gig, it was basically a friends get together) with it. In a full on gig I still prefer Serato, but your mileage may vary.