Both $S$ and $\Sigma$ are functors, so both preserve retracts: given maps $i: A \to X$ and $r: X \to A$ such that $r \circ i = 1_A$, then applying any functor $F$ gives $F(r) \circ F(i) = F(1_A) = 1_{F(A)}$.
Both $S$ and $\Sigma$ are functors, so both preserve retracts: given maps $i: A \to X$ and $r: X \to A$ such that $r \circ i = 1_A$, then applying any functor $F$ gives $F(r) \circ F(i) = F(1_A) = 1_{F(A)}$.