From my understanding, the ESS9018, for the most part is considered to be a higher end chip than the wolfsons. Many top end DACs such as the Burson Conductor uses the ESS9018. However, it ultimately goes down to your taste in signature. The Wolfsons are indeed warmer sounding while the Sabre chip is a lot more neutral and detailed. Depending on which headphones you plan to use, you may prefer one dac over the other. The Sabre chips will work better with warmer headphones such as the HD650 and HD600 and help remove the so called "veil", while the Wolfson chips will add more warmth to leaner sounding headphones such as the Q701 and maybe the DT880s.