Hallo Stanley,

there's a nice application note on web, directly from INTEL. Perhaps a bit old (1983!), but still up-to-date:

ftp://download.intel.com/design/mcs51/applnots/23065901.pdf

May be it answers all your questions? Read it very carefully, it's the oscillator bible.

Let me conclude some points: There are several ways to design a quartz oscillator. On chip oscillator of mcu is designed to guarantee fast start-up time and securely oscillating, even under worst conditions. For this, drive level and dampening are well matched. As consequence, accuracy and stability is a little bit decreased, but good enough for most of all tasks.
If you need a very stable timing base, oscillator circuit should be modified by slightly increasing of burden capacitance. Also, burden capacitance should consist of some trimmer for calibration (low temperature coefficient type!). May be, that software calibration is some better.
But make no mistake, due to temperature sensitivity of circuit you will always have a certain miscalibration.
If you use a specialized clock timing quartz oscillator, like the ones used in watches, on the other hand, you will be faced to a circuit, which is well matched to guarantee highest accuracy and stability. Drive level and dampening parameters are totally different from those used with on chip oscillator of mcu. Temperature sensitivity is drastically decreased by using different mechanisms with opposite temperatur dependency, which results in a vanishing of temperature effects. E.g. the use of burden capacitance with a very certain temperatur coefficient.

Hope it helps,
Kai