Two figures are said to be similar if their sides are proportional and the corresponding angles are equal.
Here, in ABCD and A'B'C'D', clearly,
AB = A'B'
BC = B'C'
CD = C'D'
DA = D'A'
Also, ∠A = ∠A', ∠B = ∠B', ∠C = ∠C' and ∠D = ∠D'
Hence, the two figures are similar and the first statement best describes the relationship between the two figures.