Tea snobs will tell you bags are an abomination. Convenience-focused drinkers will tell you loose leaf is pretentious. Both are wrong. The difference between the two is real but smaller than the enthusiasts claim and bigger than the convenience camp admits. Here is what actually changes when you switch.
What is in a bag
Most commercial tea bags contain "fannings" or "dust" — the small broken pieces left after sorting whole leaves for higher-grade products. Smaller pieces extract faster (more surface area), which is why bagged tea brews quickly. They also extract less selectively, pulling out tannins and bitter compounds along with flavour. This is why bagged tea often needs milk or sugar to be palatable.
Premium tea bags (the silk-pyramid kind) often contain whole leaves and behave more like loose leaf — but you pay loose-leaf prices for the privilege. At that point, just buy loose leaf.
What changes with loose leaf
Whole leaves unfurl during brewing, releasing flavour gradually. The result is more nuanced — you can taste different notes appearing as the brew develops. Bitter compounds come out more slowly, so the brew window is wider; you have less of a precise time to nail.
The same leaves can usually be re-steeped two or three times. The first brew is the brightest; the second is sweeter and more rounded; the third is mellower. Bagged tea generally exhausts in one steep.
Brewing without equipment
You do not need an infuser. A small fine-mesh strainer placed over the cup as you pour catches loose leaves perfectly well. Or brew in a small teapot and strain into the cup. Or use a paper coffee filter if that is what you have. The fancy steel-mesh balls and silicone shapes work but produce a cramped brew because the leaves cannot expand fully.
When to bother
For an afternoon cup you drink while doing something else, bagged tea is fine. For a tea you are paying attention to — a quiet morning, a guest, a tea you bought for the occasion — loose leaf is worth the extra two minutes. For black tea with milk, the difference shrinks because the milk masks much of the nuance anyway.