One thing to consider with using a crystal versus a resonator for timing is how long you are going to be keeping time. There are 10080 minutes in a week. If your resonator is off by 0.5% (worst case) your clock will be off by 50 minutes. where as a crystal at worse case (0.05%) will only be off by 5 minutes. So if I need a timer for cooking an egg, the resonator is fine, but when I come back from a week's vacation, i could tolerate my arduino based alarm clock going off 5 minutes late, but not 50 minutes late.Look at what you are wanting to do figure out what will work.
Ben, I agree with you 100% (which is why I make kits with resonators).To be fair, the following illustrates the difference between resonators and crystals:AWCR-16.00MDABL-16.000MHZ-B2Price$0.18$0.27 (plus caps)Tolerance0.5%0.05% (50ppm)Temp Stability0.3%0.05% (50ppm)10yr Stability0.3%0.05% (50ppm)The worst case scenario (end of the temperature scale, 10+ years old, and worst sample) is about 1.1% (15.82MHz - 16.17MHz) while the crystal is about %0.15 (15.976MHz - 16.024MHz). Obviously you're unlikely to see this kind of error in either component. You'd have to look it up, but I believe NASA testing showed their resonators to be within 100ppm of the target frequency from the factory. It's also important to realize these numbers are based on a perfect board layout (and capacitor matching for the crystal, badly matched load caps can severely throw off the native frequency).