A19 vs BR30

An A19 is the bulb shape everyone pictures: about 2.4 inches across, emitting in every direction. It is built for a fixture that has a shade, a diffuser or a globe around it - somewhere the light gets spread or bounced before it reaches you.

A BR30 is a bulged reflector, 3.75 inches across, with a mirrored surface behind the emitter that aims the output into a wide downward flood. It is built for a fixture that is already a reflector - a recessed can - and it exists because an omnidirectional bulb in a deep can wastes a share of its light on the inside of the fitting.

The shape codes follow one rule, per the shape guide in the sources: the number is the diameter in eighths of an inch. A19 is 19/8. BR30 is 30/8. R20 is 20/8, which is the 2.5 inch bulb small cans and some track heads take.

1. Is the fixture a recessed can? BR30 for 5 and 6 inch cans, R20 for 4 inch. The bulb should sit inside the trim, not below it.
2. Is there a shade, globe or diffuser? A19. The fixture is doing the spreading, and a reflector bulb inside a globe just makes a bright patch at the top.
3. Is the bulb visible? A19, and probably a frosted one - the comparison is in clear vs frosted bulbs.
4. Is it a track head or a spot? Neither of these - that is GU10 or R20 territory, covered in best GU10 LED bulbs.
5. Does it need to be enclosed-rated or damp-rated? That is a separate check from shape, and it is the one people skip - enclosed-fixture bulbs covers it.

Philips Ultra Definition A19 - the A19 to buy. 800 lumens at 2700K with CRI 95, which is the highest color rendering on this site in an ordinary bulb at an ordinary price. In a lamp, a shade or a globe, this is the default.
Cons: omnidirectional, so it is the wrong shape for a deep can; and at 800 lm it is a 60W-equivalent, not a room-filler on its own.

Sunco BR30 - the BR30 to buy. 850 lumens at 2700K, dimmable from 10% to 100%, damp rated, 25,000 hours and a 5-year warranty. Cans are the fittings you least want to revisit, and the rated life is the reason this one is the pick.
Cons: CRI is published as a floor, 80+, rather than a number - a step down from the A19 above; and 850 lm per can means a big room needs plenty of them.

Amazon Basics BR30 - for filling a ceiling cheaply. 810 lumens at 2700K and CRI 80, at the lowest price per can. When six cans need bulbs at once, this is the honest budget answer.
Cons: 10,000 hours rated life, well under half the Sunco's, which matters in a fitting you need a ladder to reach; CRI 80 is ordinary.

Feit R20 - for 4 inch cans. 450 lumens at CRI 90+ in the 2.5 inch shape small cans and some track heads take. The right answer when a BR30 will not seat properly.
Cons: 450 lm is modest, so a room of small cans needs a lot of them; and it is easy to buy by mistake for a 6 inch can, where it will look lost.

Buying BR30 for a lamp. A reflector bulb under a fabric shade throws a hot patch up and leaves the sides dark. The shade wants an omnidirectional bulb.

Buying by wattage equivalence alone. A 65W-equivalent BR30 and a 60W- equivalent A19 are within 50 lumens of each other. The shape decides where the light goes, and that matters far more than the last 6% of output.

Mixing shapes in one ceiling. Two cans with BR30s and one with an A19 is visible from the floor as an uneven ceiling. Do the whole run at once.

Forgetting the trim. The bulb should sit inside the can. A BR30 poking below a small trim looks wrong and puts glare straight into the room - which is the problem when LED lights are too brightdescribes.