dvorak (named for the man who created it in the 1930s) has the keys specifically arranged so that typing is quick, easy and very fast. the world record for typing was done on a dvorak keyboard, and it is much more ergonomically friendly then either abcdef or qwerty.
the problem with abcdef is this, the keys are arranged so that anyone with no typing experience and no desire to try and learn how knows where the keys are because they are in alphabetical order. however if you look at the placement of the keys its very difficult to reach some of the most commonly used keys. its not very ergonomic and its actually not that easy to type on if you are experienced typist.
also, that assessment of qwerty isnt entirely accurate. while it was designed because abcdef WAS causing too much jamming of typewriters, it wasnt because people were typing too fast, but rather that people were using one hand to type entire words. THIS is what cause the jamming to occur, so to remedy this qwerty was invented, and the keys were placed so that people would alternate which hand they were typing with after every few keys.
the best keyboard by far IS dvorak, and sorry to say this but once you use it you will agree that its just so much more comfortable. my biggest problem with abcdef though is that it takes really no time at all to learn qwerty, once youve memorized the layout of the keys it just gets easier and easier, and memorizing them takes at most 2-3 hours of just sitting down and trying. in short, my problem with it is that people who want it are just too damn lazy to learn qwerty or dvorak.