Although it is widely thought that a WF line imparts more energy (i.e. line speed) to a cast than a DT, this is not the case. Simple physics tell us the amount of energy (i.e. line speed) imparted to the line during a cast is due to the amount of energy imparted. However, although both a DT and WF line can start out with the same amount of energy imparted (i.e. line speed), the Dt line dissipates the energy much more quickly. Let me explain.
A DT line has a uniform and very long belly (center section) of large diameter line. This mean there are greater frictional losses from contact with rod guides, greater wind resistance, and that the energy of the cast is dissipated across the complete length of the cast because there is no small diameter running line to be pulled along by the front 30' of line, which means there is equal mass along the length of the line after the initail front taper.
A WF line has thin diameter running line that more or less goes along for the ride after the 30' belly (head) is out the rod, which means the energy is concentrated near the front of the line and not dissipated along its length to anywhere near the degree it is with a DT. Its thin diameter running line has less frictional losses from contact with the rod's guides and has less wind resistance too.
Thus, a WF line will stay airborne longer with the same amount of energy (line speed) imparted to a cast as a DT line.
As far as a line making a noticeable splash at the end of a cast (unless you are using heavily weighted flies or have other weight attached to the leader), it is the result of the casts energy not being fully dissipated before the line touches the water. The easiest way to make sure the cast's energy has been completely dissipated before the line falls to the water is by aiming the cast a little higher than where you want it to land. The line and leader then unrolls, straightens, and falls to the water gently.