Other than the ability to change color there is no difference in the lighting systems. The tri-cree may actually be marginally brighter in single color sabers than the Emerald or Diamond versions of the same colors.
It is. Honestly, if you have a color you're happy with go with Obsidian, I had Emerald and after the initial play-around time of trying out various colors I ended up settling on Arctic Blue and it never changed. I also found after a time that I never moved off of the standard Obsidian sound-font, either.
Which is why I buy Obsidian Lite sabers now. LOL Though I do miss the "mute" option...