Perhaps even more noticeable than the difference in sound, these two Strat have entirely different necks. The 60 has a slim C profile with slab rosewood fingerboard, whereas the 56 has a large soft V or boatneck profile (soft V to C transition, starting around the 5th to 7th frets) and is one piece of maple.
Both necks feel great, but I wish the depth of the 60 neck (approx 0.81" @ 1st fret to 0.93" @ 12th fret) was closer to the 56 neck (approx 0.88" or 0.90" @ 1st fret to 0.98" or 1.00" @ 12th fret).
Kelsey's description of the two guitars was bang on to what Bruce from Wildwood Guitars described. For that reason I chose a '60 NOS Stratocaster from Wildwood with a 9.5" radius. This guitar is simply amazing, I'm totally happy with my first Custom Shop Strat that I got week ago.