The trick is to match the screen to three things:
1. The room
2. What you watch - and when
3. The projector
We’ll consider the HW40ES - 1700 lumens, which, at least by Sony’s “intent” is their projector geared for less of a home theater (dark walls and other surfaces, very good lighting control), than for a living room, media room, bonus room, family room…basically less ideal rooms. (Their more expensive HW55ES is better matched for a true home theater/cave.) These other rooms typically are without the ability to block out all outside light during the daytime The darker the surfaces in your room, the better.
In a previous home of mine (photos on the right), I took near white walls and ceilings and darkened the ceilings (same off white shade) by several shades. They still appeared to be “off-white” because they were still the brightest surfaces in the room. I also took the walls from an "off-white" to a rust color. Oh what a huge difference it made. For that room I used a Stewart Firehawk, which is pretty good at rejecting side ambient light.
I’ve had projectors set up in such rooms. One can get those rooms dark enough tor casual viewing - sports, most HDTV in general, but too bright to really be ideal for viewing movies.
You’ll have to decide if movie viewing will be reserved for when you can keep the room pretty dark. That would affect your screen decision.
If you have one of the latter types of rooms, and you are planning to watch a mix of general HDTV and movies, then you’ll want a screen that can “help out” with dealing with ambient light. That’s typically what are known as High Contrast gray screens. (Gains from 0.5 to 1.3). They can reject a fair amount of side ambient light, providing a much better picture. Still, movie viewing will be best at night, when you have full lighting control even with the right screen, if your room has a fair amount of ambient light (I’m not talking bright, I’m talking modest amounts - ie light leaking in around dark window shades…