For ultimate audio quality, which is the major consideration in a home audio playback system, so far, I slightly prefer the Crane Song Solaris. Having said that, it's early days and those who believe "break-in" is a real thing may tell me that the Mercury needs a few dozen more hours of playing time to perform its best.
On the other hand, the Mercury handles PCM sampling rates up to 32/768 and DSD4, while the Solaris is limited to 24/192 PCM.
Also, the Mercury offers two AES inputs (one of which can be used as dual-wire), two coaxial SPDIF inputs and two optical inputs, while the Solaris offers only one of each. Read more
Both, of course, offer a USB input.
Like the Solaris, the Mercury offers two sets of balanced analogue outputs, one fixed, the other variable, so both can be used as a monitor controller without a separate preamplifier. The Mercury also offers a word-clock input, while the Solaris does not. On the other hand, the Solaris does its own internal digital-to-digital conversion (not defeatable), which may be why no word-clock I/O is provided.
I could happily use either DAC to drive my Meyer Sound Labs X-10T monitors, but it's even better to have both available!