More or less, The flash duration is about the same but there is less light output and so you use less power and there is less to replace and so recycling is quick. Also you can get many low power flashes on the intial charge. On the AF400T, you could select 1/25 power. With that, you could get about 10 shots with the motor drive running.
Another advantage is that you can reduce the power which makes balancing fill in flash much easier. Effectively you decide on the aperture rather than being forced to use the one "effectively" set by the flash.
Kim
Originally posted by SirJangly Oh is the 1/128 power just a very fast flash?