Small coils are typically more tolerant to variations in sample conductivity (e.g. salt) than are larger coils.  While this is not a rationale for comparing the absolute S/N of one probe technology against another (such comparisons should be made using the sensitivity arguments explained previously), greater salt tolerance does imply that the degree of intervention required to adjust (e.g. tune, shim) the probe between sample runs is less, and that the S/N obtained using a salty sample and a microcoil probe will be closer to the S/N obtained using a non-salty sample.  This translates to ease of use and greater experimental consistency for the spectroscopist, faster analysis due to less need for shimming (and consequently reduced shim settling times) and re-tuning between samples.