I can't speak to the attributes of the 908, but can tell you that the 3913 is considered to be one of the finest compact nines on the market. Mine (pictured below)has functioned flawlessly since I bought it new in 1993. Good luck in your search for either gun!
So far my 908 has been flawless and surprisingly accurate. Bought it used in Great shape and have fired ~700 rounds. Only JHP I have tried are Federal HST 124 +P and 115 9BP.
They share the same grips and mags, so I would say yes they are the same grip width. But the slides are contoured differently and will not share the same leather.