In terms of price, they are aimed at the same market. In terms of quality, well....
If you do a search for electrostatic headphone amplifier schematics, both commercial and DIY, you'll find a lot of resistor loaded output stages, you'll find several constant current loaded output stages, and you'll find some transformer output stages, but you won't find any choke loaded output stages. The Woo WES uses choke loaded output stages. Now, there are two possible reasons why they are unique in this respect. The first is, they have a patent and nobody else can use it - however choke loaded output stages have been around for a long time, so that's not it. The second reason is, they don't know what they are doing and are using an expensive topology that is demonstrably inferior for this particular purpose. See my thread on current requirements for electrostatic headphone output stages for infinite gory detail on why current loads are the optimum way of loading output stage active devices from a strictly engineering perspective.
Second, the WES has a passive power supply rather than a regulated power supply. Now, Stax also use a passive power supply, however they are much cheaper and much smaller so there's a good engineering reason for that. In an allegedly state-of-the-art design, there is no reason NOT to use a regulated power supply since the ideal power supply provides a perfectly stable, noiseless and unvarying voltage regardless of the demand on it, something no passive supply can do, and something a regulated supply is much closer to doing.
In other words, IMHO the WES is state-of-the-wallet, but not state-of-the-art.