Referencing the parent's comment, this lets you replace subpanels or even individual (sub)pixels as needed --- with a TV, if the panel is damaged, it's all or nothing.
I wonder what the weatherproofing (particularly heatproofing) on these things is like.
LEDs are more sensitive to heat than CRTs or incandescent lamps, but less than LCDs.
1) a LED "wall" is far brighter than a comparably sized TV, that's important when you place stuff high on a building
2) An ordinary TV is designed to be looked at from the front, a slight angle skews the colors and if it's extreme enough the screen gets totally unreadable.
3) A TV eats up tons of power, a LED wall not so much.
Regarding point 3: At 150 modules consuming about 25W each, your LED wall is consuming about 3750W max. An 80" TV will consume about 300W.
Power consumption of the LED wall will, however, be highly dependent on the displayed content. A white screen will consume most, a black screen basically nothing, but displaying only dark images is not exactly what LED walls are usually used for.
The equation is simple: The brighter, the more power you'll need, and an LED wall is, as you say, far brighter.
With a LED wall, only the lit pixels will consume power - the backlight of most TVs is full-on all the time. Only exceptions (iirc) are OLED TVs where the pixels themselves generate the light, and TVs which have their background light partitioned to achieve true(r) black by turning down all-black areas.
I wonder what the weatherproofing (particularly heatproofing) on these things is like.
LEDs are more sensitive to heat than CRTs or incandescent lamps, but less than LCDs.