Price is the main factor. I use the proteus when the mood stikes me, not an every day thing. Usually when I want to have more focus on relaxing / learning. The light show keeps me from drifting off too far and I have even not used the sound effect only the light show and paraliminal tape.
The proteus comes with about 49 presets at least 12 of them are suited to learning a couple for learning with tapes. So you don't have to create the right soundtrack or light show.
The thought stream sounds interesting but I don't need another toy... there comes a time when you just need to make the commitment to use the toy/tools you already have without getting sidetracked by another. 
Alex
