Comparing Apples and Oranges
A two-handed kettlebell swing whose purpose is to emulate or replace "speed" deadlifts in a Westside-style powerlifting program is not the same thing as either a two- or a one-handed kettlebell swing done for GPP purposes.
Power Output, Apple to Apple
Steve, my post address the Power Output Comparisons; Heavy Kettlebell Swings rivaling Olympic Movements.
The Power Output of the Heavy Kettlebell Swings rivals Olympic Movement.
Speed Deadlifts
Power Output of Speed Deadlifts dwarfs in comparison to Heavy Kettlebell Swings and Olympic Movement.
While some Power can be developed with "Speed Deadlifts"/Power Deadlifts it is not the optimal method of demonstrating or increasing Power.
Research by Dr John Garhammer (which I have noted in other post) found that even when Deadlift load/percentages were dramatically decreased, "Speed/Power Deadlifts were even close.
With that said, the movement pattern and muscle involvement of Heavy Kettlebell Swings is similar to the Deadlift.
Employing Heavy Kettlebell Swings and/or Olympic Movements is an effective training tool for increasing the Deadlift.
GPP
General conditioning is determined by the Training Protocol, not the exercise choice. Thus, any exercise can be effectively employed as a Conditioning Exercise.
One Or Two Hand Swings
The Kettlebell Swing utilizes the largest muscle of the body, the posterior chain. To effective overload them, a greater load is needed.
Obviously, a Two Hand Swing allows a lifter to use more weight than a One Hand Swing.
Thus, the Two Hand Swing dramatically increase the overload to a greater degree than a One Hand Swing. That applies across the board: Power, Hypertrophy, GPP.
Matching Training to Goals
Steve Freides said:
Advanced, competitive athletes in any sport, including powerlifting, should take advice from their coaches about how to use lifting weights to enhance sports performance. Beginning and intermediate athletes would do well to follow the guidance of Kettlebell Simple and Sinister.
Many here on our forum train for general health and fitness. Some participate casually at a sport. Many, perhaps most, here either don't have a coach or don't care to direct their weight lifting only towards improving their sport-specific performance. For this group, in which I include myself, we will have to say, "Your Mileage May Vary." Experiment to find what works best for you.
Match Your Training To Goal and Your Training Age/Experience
The Goal and Training Age of a lifter need to be taken into consideration in writing a program.
Employing Heavy Kettlebell Swings is geared for some intermediate and advanced lifter in pursuit of increasing Limit Strength and Power in Powerlifting or other sports.
Experimentation is fundamental to finding out what work and gaining knowledge. However, some rule do apply.
Kenny Croxdale