I have just posted a new article on English Cut, "Straight or Crooked".
http://www.englishcut.com/archives/000072.html
I hope you find it informative.Basically the fit of a straight coat has less material forward of the neck point on the front edge. This gives the jacket a slimmer feel, showing more shirt, especially on a double breasted. Also another characteristic is that the collar although fitted well, sits lower around the neck. This again shows more of the shirt and gives a slimmer feel to the wearer. This cut gives the feeling of a more youthful cut simply because as we age we invariably gain a little in the front. We then obviously require more material to compensate, or less when we are slim.
A crooked coat has basically the opposite characteristics. The coat should always fit neatly around the collar, however it will generally sit higher, showing less of the shirt collar stand. Also even if the coat is slim through the side seams it will still be easy in the front. There will be less shirt showing, again especially on double breasted.
Thank you.