I don't think it is really fair to compare the 2 at this point. The ESS Sabre Reference chip was released 2 years ago, while the AD1955 has been around for over 10 years. The ESS 9018 is a very sophisticated DAC chip featuring an innovative onboard SPDIF receiver, a unique upsampling/oversampling method, and programmable digital filters. It can be used in either voltage or current output mode, and requires a very specific following output stage to achieve maximum performance. I just don't think there has been enough time for a lot of the traditional high end companies to design and release CD players or DACs based on this chip. I bet the AD1955 was in a similar position when it had been on the market for only 2 years.
You can find examples of each chip in both lower and higher end DACs: At around $300 you have the Audio GD NFB-11 (ES9108) and the Matrix Mini-i (dual AD1955). On the higher end of things we have the Audio GD NFB-7, Anedio D1, and Buffalo-II implementations (ES9018), and the Berkeley Alpha DAC among many others (AD1955). Clearly both chips are dependent upon other factors to determine their level of excellence, and clearly both have plenty of potential.