Is there a difference from one battery to another? I've always gone OEM in everything I replace or repair (although I know it cost more). Are some of the choices people made based on a belief that the new battery is 'better' than the OEM, or is it more a financial decision?

I've tended to go OEM out of a belief (maybe misplaced) that the battery that the manufacturer picked or designed for the car must be better than the others. Is that not true - if any battery will do, then I'll go for a savings too.