We used a sheet and borrowed a projector for a couple movies over the summer for years. Then we saw the inflatable screen as the weekend special at home depot and picked one up.
As @Ladeback69 said lumens are what you need to be focused on if your going to watch outside. I would recommend nothing less than 2500. Mine is 3000 and if I had to buy one again I would go higher. Our backyard is pretty shady, but you have to wait until it is almost dark to see the screen well enough to enjoy the movie. I use my ps3 or apple tv using hdmi for video and paired with a sound bar using a fiber optic cable for sound. The wii is also really fun to play on the 12' screen.
If you're trying to watch during the day or dusk you need to look at a rear projection screen and have at least 5000 lumens and there your going over $1000 easy.
I travel with my small all the time and love it. I do have an eggCARTen which makes it easier to move with one person or a breeze with 2 people. If I was in the market I might look at the minimax, but the small is the perfect portable egg for me.
I was trying to find one of my posts without signing into the forum and ran across this. I'm still around and cooking on my large and small eggs. I just don't have as much time to make the detail posts I like.
I try to pop in every now and then and will try to make a post if I do anything worthwhile.
See I've still got them and the picture to prove it!