It is important to not get confused about which kind of 4 Link you are talking about. The 4 link that I have and RMS sells is a triangulated 4 link that has a set of diagonal bars, usually on top of the rearend, and two lower straight bars. The top bars that angle in toward the centerline of the car help in the lateral movement of the reareand. The two lower bars that go straight help the rear maintain a true up and down motion.
The four link that you will hear about when talking about a drag racing application has all four bars going straight and may employ a panhard bar which is a lighter rod that keeps the rear from swaying.
In a drag racing, a triangulated four link would be less optimal than Cal tracs. I don't know about the ladder bar and "traditional" 4 link debate but I have seen leaf spring cars beat both. It really is all in the way it is set up. Set up correctly, ladder bar and "traditional" 4 link cars will beat a leaf car if everything else equal, but it is proven that just because you have some "other" suspension doesn't mean you'll be faster than this or that. You have to tune it.
So, it's important to know which 4 link you are talking about and it's important to have a tuned suspension (not just "parts" under the car).
If I were going drag racing, I would opt for a ladder bar suspension. It's easier to tune and more robust.
