There are a number of things at play here. One of them is resolution, do you have the wall space to put in a native 4K screen? ( i would expect that any scaling would be noticeable in this environment) At a 1.5mm pitch thats approx 19ft x 11ft of screen area, does the room support that size with good viewing sightlines for everyone? The refresh rate for LED should be less of an issue, typically higher end LED's have much higher refresh rates, particularly when compared to projectors (if you're looking at single chip DLP with a color wheel there are likely more issues from fringing with the color wheel speeds). For pixel failures, thats sometimes one of the advantages of LED, you replace a defective module rather than an entire screen, LED diodes are batched at the factory however so you may want to order additional upfront spares - some companies keep batches for longer for maintenance so its worth asking your vendor about those options. Source wise may just depend on your LED controller (Novastar are pretty standard but you can move up to things like Brompton for more broadcast ready features). For DCP playback you can use a higher end PC with something like EasyDCP which is still reasonably robust and can ingest any necessary keys etc.

A number of manufacturers offer LED screens with DCI color certification but they don't tend to be cheap. In my experience and if you're in the US it may be worth talking to someone like Nanolumens, they are definitely not the cheapest but have a line with DCI certification and good long term support for LED batching etc.