After getting my 6906 I was really clear as to why this is considered such a good carry gun. Then I got my 4006 and quickly learned the reason. Since I don't carry, the extra weight of the 4006 is not an issue, but if I did.........
More than the length of the barrel or the size of the grip, the biggest reason the 6906 is more appropriate for concealed carry over the 5906 is the weight difference. The alloy frame of the 6906 makes it a much better choice for ccw than does the steel frame of the 5906 because it is considerably lighter. Being shorter and less bulky is icing on the cake.
Interesting, my 5906 has an alloy frame. I seem to remember that the difference in weight unloaded is about 9 ounces.Could be very wrong here of course.
Can someone post a picture of the 6906 with the flat bottomed 5906 mag baseplate? That sounds like a nice concealment addition as I've never like the hooked baseplates.