wickidwombat said:
I disagree I find the images sharper using second curtain as the sharp image is exposed over the top of any movement blur not the other way around
Well you might disagree, but that doesn't make you right. You have two exposures, ambient and flash, the two exposures are exactly the same, the burn in is identical with first or second curtain sync for the same ambient exposure, one is not "on top" of the other as the pixel information relays a two dimensional image, each pixels brightness is the result of the combined two exposures. Further, any movement blur is outside the sharper flash image, the pixels that record the blur are pixels that didn't get any flash exposure, so how can it matter when the flash fired?
There are a couple of good reasons for second curtain sync, but imo your examples are not one.