The ppm portion of their spec is meaningless in the context of digital audio (as long as it is withing 100ppm you are fine), but the mention of phase noise is correct, as this directly translates to jitter. Measuring at 10Hz is a plus as well. I don't really understand all of this myself, but most will only publish down to 100Hz. The lower the frequency, the higher the jitter/phase noise (at least according to Jocko and gmarsh).
Of course that is just the crystal spec... I think what you do with it has more of a determining factor.