Ideally you would want the steering arm parallel with the front half of the leaf spring or slightly lower in the back since the center of the axle is lower than the leaf spring. For a vehicle that is driven on the road only I think a push pull system is just fine, because it doesn't put a side load on the leaf springs.
Now when you start going offroad and/or getting a lot of articulation then a crossover system with a much longer arm will have less bump steer over longer wheel travel range. But actually, for just street driving, a stock system may have less bump steer because the axle moves up in down in a forward arc with the leaf spring, not a sideways arc(that's why most vehicles with crossover steering also have panhard bars). It's just that too much travel on that short of arm (stock) creates too much angle, which causes issues.