Which flavor of tea you like is often subjective, but I would like to briefly walk you through "objective" understanding of tea quality. This is general idea and not necessarily all true in specific applications.
This is mostly visible in loose leaf tea before and after brewing. Take a look at your tea leaf.
Harvest can determine the base quality. Generally young tender leaves are plucked depending on what quality is desired. If the harvest include older leaves, they tend to express more substantial bitterness and astringency, which are generally not preferred for this type of harvest.
Hand Plucking or Mechanical Harvesting
Mechanical or machine harvest tend to cause uneven harvest. Some young leaves and some younger leaves. For example, ones at the level of the cutting surface is plucked full size while ones a few inches below the cutting surface is plucked only at the tip and ones flushed early may include slightly older leaves. Often times plucking surface is cut even before harvest so no old leaves are harvested. and younger leaves included in your harvest does not degrade the quality much like older leaves. It could be better. The mechanical harvest does not retain leaf shape completely.
Although hand plucking generally acheive better quality due to more selective plucking, it is also influenced by pluckers' experience level. Inexperienced pluckers do not know subtle balance of hand pressure and tenderness of the harvestable leaves for desired tea quality. Bad plucking tends to damage leaves and cause faster degradation.
Harvest timing also determines the quality. Spring harvest tends to be higher quality since cool whether slows hardening of the tender leaf. Even within spring harvest early harvest generally holds more delicate flavor compare to later harvest.
There are some regions that found a way to take advantage of seasonality to process and express different characteristics. In such case, spring harvest, summer harvest, winter harvest are all interesting to compare, or maybe not compare but enjoy separately.
High altitude tends to have higher quality than low land (sea level) because of lower temperature keeps the young succulent shoots from hardening although low land tea might grow faster because of higher temperature. Elevation too high can be problem due to frost damage. Tea is basically sub-tropical plant and does not like frost very much. Certain varieties are bred to withstand frost, but they may compromise some qualities.