Four questions, about a minute. Answer each and the card at the bottom says whether to stay with a TV or go for a projector, and what kind.
Answer all four questions to see your result.
A projector gives you size. A TV gives you brightness, convenience and a picture that survives a sunny afternoon. For the price of a decent 55-inch TV you can get a projector that throws a picture well past 100 inches, which is why it feels like a different kind of film night. But the projector pays for that size in light: it makes its picture by shining onto a surface, so every bit of ambient light in the room washes the image out.
That is the whole decision, and the four questions above are just ways of weighing it. How dark the room gets matters most. Everything else, from the wall to the budget, decides which kind of projector and which kind of screen.
Keep the TV. If the room is bright, the screen is on all day and the wall is crowded, a projector will frustrate you. Put the money into a better TV or into sound. A dedicated soundbar with a centre channel is the cheapest way to make films feel bigger, and it works in every room.
TV plus a good soundbar. If you are on a modest budget and the room is only sometimes dark, this is the safe middle. Most of the thrill of a film night comes from sound, and it is the part a TV does worst.
A Full HD projector and a screen. The first real step up. A bright model, around 3,000 lumens or more, copes with a dim room, and a proper screen is worth the money: a wall can work, but a matte white screen keeps the picture even and the colours honest. The Epson EH-TW840 in the picks is Full HD with 4,000 ANSI lumens and a 3LCD design, so it suits a living room with curtains drawn rather than a blacked-out cinema.
A 4K projector in a dark room. If you can get the room properly dark and have the budget, 4K detail and HDR support pay off on a big picture, because pixels you could ignore on a TV are easier to see across 100 inches. The BenQ GP520 in the picks is a 4K HDR model rated at around 2,600 ANSI lumens, which is enough for a dark or dimmed room but not for daylight.
Brightness figures are marketing's favourite number, and they are not always measured the same way. Look for ANSI lumens, which is a standard method, and be sceptical of unbranded boxes that claim thousands of lumens for pocket money. Contrast, lens quality and fan noise matter just as much, and none of them show on the box. Read independent reviews for any projector you are close to buying.
Brightness also has to be shared across the screen size. The same projector looks dimmer on a 120-inch picture than on a 90-inch one, so if your room is not fully dark, choose a smaller picture rather than a bigger projector.
Ceilings and walls count: a dark ceiling and walls improve contrast more than most settings. Sound is separate: a projector's built-in speaker is a convenience, not a cinema, so plan for a soundbar or speakers either way. And distance matters, since the projector has to sit a specific distance from the screen; the throw-ratio explainer on this site covers how to measure it before you buy. Prices change, so treat the budgets above as rough guides.
Change one answer at a time, say the darkness of the room, and watch the result move. If one answer flips your result from projector to TV, that is the one to take seriously. Most people find that light, not money, is the real limit.