The main difference between loose teas and bagged teas is the size of the leaves. That's what effects the resulting cup of tea.
When the tea leaves are broken up, those oils can evaporate, leaving a dull and tasteless tea. Typical tea bags are filled with the tiniest pieces of broken leaves, called fannings. Take the time and you can taste the difference in loose tea on sale.
Loose Leaf Tea, Buy Loose Tea