I voted for the wider sign, mostly because I would prefer to see the graphics on top.
Your project has given me a new appreciation of how difficult hands are to draw, particularly from the angle that the viewer sees when the other person is signing the word "sign."
I have a new appreciation for the "power fist" icon as well. It seems hands are especially difficult to draw in "icon" type drawings. Larger figures like a man, woman, wheelchair, telephone handset, are easier to sucessfully reduce to icon type drawings.
The picture PFH doesn't say "sign" but it is a pair of hands. If fluent signers think that gets the idea across and you don't have to deal with iconizing an almost impossible to draw hand position -- sounds like a win!