Watched the 2012 Texas Bass Classic last week, top 15 anglers from the FLW, top 15 from the Elite series, and 5 sposorship spots, they're on Lake Conroe, which has a one fish limit, so the solution is each boat has a marshall who weighs the fish, gets agreement from the pro, record the weight and release the fish. They use Bogas.
I went through several brands of digitals before getting a Boga. Heard good things about the Chatillons also. If you want reliable, consistent weights, get a good spring scale, if you want a "ballpark" weight get a digital.