The silver Zeiss Ikons have a paint finish. Chrome Leicas are indeed chrome. If its paint, Leica will say so in their literature. The new Steel-Gray finish on the M9 is paint, for example.
The Zeiss Ikons have metal top and bottom plates. The Voigtlander Bessa L, R and T have plastic top and bottom plates. Bessa models starting with the R2 have metal top and bottom plates.
Chrome Leicas (and chrome Leica lenses) are heavier than their black counterparts. I had my M3 painted black by Robert Jagitsch. The chrome plating was removed but I elected to keep the nickel plating underneath for two reasons. First, the paint will stick better to nickel than to the bare brass. Second, leaving the nickel plating kept the weight of the camera up. I just love the feel of the heavier chrome equipment; especially the lenses.