We install both and I personally have a few projectors in my home, one is the the Epson LS300 short throw. Currently, that is new and replaced a TV and being shown on the wall temporarily. Each has its pros and cons. In general I like the long throw projectors more except for classrooms and ambient light.

Long throw has better screen uniformity and doesn't have the bowing that a short throw has. It is also easier with most ambient light rejecting screens. A short throw in an ambient light scenario definitely needs an ALR screen designed for a UST. The Silverstar will not work. what Long throw HT projectors don't have in general is lumens. This LS300 I have is BRIGHT and even watchable with a south facing bay window on the side. Not the best picture but still watchable. At night or at dusk time it is stunningly bright and a lot of people have commented on how great it is.

The 4K Sony you are considering might not be the best projector for the job if dealing with a good amount of light. The JVC-NX5 puts out a few hundred more lumens and IMHO has better picture quality with its tone mapping. But if you are dealing with ambient light you could put in an Epson 3800 in dynamic mode (knock down the green a bit) and it would be preferred. The JVC and Sony will definitely look better in the dark but the added brightness of the Epson will win when watching with ambient light. if you need more brightness than something like the Epson 3800 than usually it is easier to go with a high output commercial projector.

If ambient light is the majority of their viewing than UST with ALR might be the best option because many of these UST projectors are very bright. This LS300 is putting out a real 4000 lumens in its dynamic mode and that brightness will make a beautiful picture with a good screen. That's more than double the JVC and triple the Sony and that is noticeable and nice. The LS500 (4K) is about the same brightness but requires a bit longer throw. That is why I went with the 300 in my home as it fit where I needed. It takes a 4K signal and down converts to 1080 but still does HDR which is nice. In the end that is a discussion with the client and how often they watch in the dark vs with ambient light. Then decide what will work best. I will be curious to see what you decide.