Which is objectively a better word. Ah Americans - twice the syllables, twice the letters, and it doesn't even flash!
Reminiscent of "elevator", except that has four times the syllables! "Transportation" (transport), "burglarize" (burgle), "garbage collector" (dustman), "apartment" (flat)... I'm detecting a pattern.
They can flash by pressing the button. On some flashlights partially pressing and releasing the button flashes the light off and on. That's a notable difference from, say, lanterns where you need a cover or shield for signalling.
The problem with "torch" is that there's already a thing called "torch", and now I don't know which thing you mean. The word "flashlight" has avoided critical ambiguity in many of our Indiana Jones movies.