CREATE TABLE table_204_177 (id DECIMAL, "player" TEXT, "years played" TEXT, "total w-l" TEXT, "singles w-l" TEXT, "doubles w-l" TEXT)

who had a better singles record , boo kil or seung bok ?
SELECT "player" FROM table_204_177 WHERE "player" IN ('choi boo-kil', 'baek seung-bok') ORDER BY "singles w-l" DESC LIMIT 1
SELECT "player" FROM "table_204_177" WHERE "player" IN ('choi boo-kil', 'baek seung-bok') ORDER BY "singles w-l" DESC NULLS LAST LIMIT 1