What's your take on oscillator modules vs discrete crystals?
If you're asking about audio, I tend to think the packaged oscillators sold to improve jitter performance are overkill the vast majority of the time. I have seen $100 DIY modules that are basically rebadged off-the-shelf oscillators up to $10k+ clock boxes with fs jitter performance. A recording studio may use a master clock box to synchronize everything, but I really doubt they are paying audiophile prices for it. Usually one of the components has buffered clock output they can use.
Bearing in mind my work is not audio, for us and our customers it is basically a "make or buy" decision. A crystal circuit is cheaper, assuming the amplifier is on-chip, but usually has lower performance. As long as the performance is good enough to meet spec and the layout (and chip) design are good then a crystal works fine. A pre-packaged module has all the work done for you, has greater slew rate and lower output impedance into the chip's clock input, and so may offer better performance -- at a substantially higher cost. It also usually requires a filtered power supply rail, and a few support components for enables and such, so component count and board area might not be much different than the crystal circuit. Beyond that, you can get much higher-performance packaged oscillators with lower noise and features like temperature control (built-in ovens), programmable frequency and output voltage, and so forth. For a consumer audio device, I'd expect a crystal into a DAC (or whatever) chip would be good enough and cheaper, always assuming the board designer does due diligence on the layout requirements, both for parasitic elements and things like thermal considerations.
Things that can go wrong with a crystal circuit, besides the long traces mentioned above, include things like placing the crystal too close to a SMPS regulator that couples noise into the circuit, not shielding the crystal traces from adjacent signals or noisy power planes, and placing it close to a heat source that may be the device it is connected too -- sometimes putting the crystal on the back side helps if the device consumes a lot of power. And so forth. I have just enough experience designing oscillators to know there are a lot of tricks and sneaky "gotcha's" that takes an expert with lots of experience to catch. Without that, or access to it, buying a prepackaged oscillator may be the best solution.
Many crystal and device manufacturers provide design guidance and sample layouts that need to be followed closely to prevent such problems.
HTH - Don