Answer to #1; I don't think one is any better than the other. I have had a Psychedelic (Purple) one for close to a year. He lives in my 33G semi cube. He has doubled in size in that period of time. Just don't try and keep them with Sixline wrasses, as you may be asking for trouble.
Answer to #2; You should not have a problem. It would be a particularly stupid fish to allow itself to be caught by a shrimp. Mine is in with a Stenopus zanzibaricus, and has never been caught.
