Brenda gave you all kinds of good facts, so let me address your question from a slightly different perspective.
My short answer is: There are no significant advantages, or disadvantages, in living in a particular zip code unless you have school-age kids and want to drill down on the performance/satisfaction ratings of varous schools.
Zip 30359 is the City of East Ellijay, so you'll pay more in property taxes there than you will in un-incorporated Gilmer County. The same is true if you buy a home within the city limits of Ellijay, which is located entirely in 30540.
All of Ellijay and East Ellijay have county water and sewer services as so some parts of unicorporated GilmerCounty. County water will save on your homeowner's insurance, But, over time, the combination of water/sewer and insurance costs may well be less if you have a well.
The lesson here, I think, is that every buyer and every property is unique, so a more fully-informed answer to your question means knowing more about your hopes and concerns.