You can further reduce the difference by passing Expr by pointer in the C version. At that point I think the only difference in the assembly is the order in which the cases are handed.
cmp ecx, 1
je .LBB0_3
cmp ecx, 2
jne .LBB0_2
Oddly, both sources seemed to be quite sensitive to match switch and enum reordering, resulting in very different generated code. Possibly something to look into further.