Same way a Suzuki, Kia, Honda, Lexus , Rolls Royce differ.. they are all cars and will get you there, but some are more expensive, have more options, perform better and are built better. a $300 screen is just that a white piece of vinyl stretched over a flimsy frame. The fabric is thin, and possibly not color neutral but if you only have $300 it will fit the bill
A $3000 screen is going to have a solid, well built, easy to assemble frame, with a large selection of fabric choices to fit the needs of the installation.
If you are happy with your screen, and the new room is similar in color, with the same size screen you have, why look at something unknown? If it is a good product buy it again!