A video wall is several panels driven as a single surface. Two very different things go by the name: a grid of LCD panels with thin bezels, and a seamless LED wall built from tiles with no gaps at all.
The choice is mostly about viewing distance and budget. LCD grids are far cheaper per square metre and perfectly good where viewers stand back (lobbies, control rooms, corporate atria) because at distance the seams stop reading. LED walls have no seams and can be built to any shape, which is why they win in retail flagships and stages where people stand close.
The caveat is that the wall is the cheap decision and the content is the expensive one. A 3×3 grid is not a big screen; it is an unusual aspect ratio that almost nothing is authored for. Stretching 16:9 video across it looks wrong, and content designed for the exact pixel dimensions has to be made specifically, forever. Budget for a content pipeline, not a one-off launch reel.
Second: heat, weight and access. Video walls need structural mounting, real ventilation, and a way to reach a failed panel in the middle without dismantling the array. Those are building decisions, made long before the screens arrive.