Looked into this a few years ago and found that sony seemed to be ahead of the game in that department at the time. If you look on cameras.co.uk at the camera reviews, you will find that shutter lag times are listed and there is a shutter release comparison table, just had a quick look on there to make sure that it still existed, but did not look in detail to compare, but have a look and see if it is of any help.
Jon