A good screen also will have a wide viewing cone (the area to sit where the picture looks best. A wall will hotspot a lot more.
A compromise between the two, for your DIY types - use a wall paint such as Goo.
You can mask out an area, paint it, then even paint a black border around it if you like. I'm not a big fan of screen paint, and last I looked there was still a bit more hotspotting than with a screen. That said, the screen paints are supposed to be a lot better than your basic home wall paint when it comes to hot spots, etc.
You can get pull down screens starting around $100. (Although $200 is more typical with major brands). Warning though, you'll have to pay a good chunk more though to get a pull-down screen with tensioning. Let me put it this way. If you go pull-down screen, and actually plan to lower and raise it a lot, get tensioning, or it won't last you very long at all. Without tensioning, soon you'll end up with wrinkles, really waves, and they are extremely distracting when you watch.
Fixed wall screens are theoretically the best, and stay nice and flat, but they cost more, typically starting around $400 but most major brands in the $500 - $700 range. With a portable like system, somehow, pairing it with a fixed wall screen seems less likely, but, perhaps in that bonus room?
You can also find pull-up and tripod stands. Epson offers up a tripod stand called the Duet. It is adjustable in width so you can set it for 16:9 or 4:3. It works well, we commented on it in a review of an older MovieMate, a couple of years ago. It sells for $149.99 (MSRP) from Epson, and might be less from a dealer.
The screen is a relatively small 80 inch diagonal in 16:9 mode, which combined with the large amount of lumens the MovieMate 60 cranks out, makes for some good viewing, even with a fair amount of room lighting.
Most folks will just want a pretty standard screen surface - a typical white with slight gain, say 1.1 - 1.4 gain. Still if you want to attempt to eliminate some washout from side lighting, you can go with a high contrast gray surface, which almost all screen manufacturers make.
Finally, the MovieMate pairs beautifully with those inflatable outdoor screens. I've got one, and while I haven't used the screen in a while, I did use it with a previous MovieMate. It's a killer combination, and the MovieMate has lots of lumens for those big inflatables.