Coffee quality is influenced by a number of factors, as mentioned here such as harvesting, coffee processing, coffee varietals and growing altitude just to name a few.
Generally, higher altitude coffees have superior flavour. This is because in cooler temperatures the coffee fruit matures more slowly and yields denser beans which concentrate the sugars, organic acids and other compounds that create the flavour profiles found in quality coffee.
Anything growing above 1500 masl (meters above sea level) is quite a high growing region and will generally exhibit a refined sweetness. While lower down at 1000masl – 1250masl the acidity is mellowed significantly and more earthy tones are found, think Brazil or India.