The crystal's frequency stability is given by the Q-factor. The Q-factor is the ratio between the energy stored in the crystal and the sum of all energy losses. Typically, quartz crystals have Q in the range of 10,000 to 100,000, compared to perhaps 100 for an LC oscillator. Ceramic resonators have lower Q than quartz crystals and are more sensitive to changes in capacitive load.
Several factors can affect the frequency stability: Mechanical stress induced by mounting, shock or vibration stress, variations in power supply, load impedance, temperature, magnetic and electric fields, and crystal aging. Crystal vendors usually list such parameters in their data sheets.