First, the following general considerations may be helpful.
http://www.differencebetween.net/technology/difference-between-oscillator-and-crystal4/
Next, the following items may be considered when comparing real / available crystals and oscillators :
1.
Cost. Crystals usually are cheaper.
2.
Package Size. It depends on real considered parts.
3.
Start-up time. It depends on real considered parts.
4.
Additional pins, elements.
Crystals require extra circuitry (capacitors), that can affect the frequency accuracy and stability.
Oscillators require power voltage (and GND), but their accuracy and stability are specified.
5.
Drive Level – when using an external oscillator its signal level should match
input specs of processor. No need for such considerations for crystal.