I respectfully disagree on the use of a whip finisher being slower than using the loop method, or the hand/finger method of tying a whip finish. The Materelli style whip finisher will tie the whip finish faster and place it more accurately than either the loop or hand methods. All it takes is a little practice.
I will grant you that the vast majority of whip finishers on the market, which are copies of the Thompson whip finisher, are slow and clumsy compared to the loop method or hand/finger methods. The Materelli style whip finishers are in a different category altogether than the Thompson style ones and allow you to produce the whip finish very quickly and accurately.