Having the best fish finder is not as important as being able to read a fishfinder. Color is definatly the only way to go. IF you have it set right, you can tell different species of fish, but mostly what type of bottom you are on. The ability to tell between sand, mud, and shell can make the difference when fishing.
Better scopes cost more more many reasons. Usually the better ones have better gain, clutter and interference rejection.
Stay away from the sounders that show the fish with smily icons!!!
There used to be a way to get the first NorthStar sounders to show targets as the fish from the simpsons...
As with anything... the best way to get a feel for what you want is using other people's stuff. Demo modes are useless, and often show the screens at way better than you could ever get in real life. I rember one of the lesser brands showed a 3D picture of a boat... you could even make out the registration numbers... in honsety, i don't know how a scope can tell color... but the demo showed it!!