I can't think of any examples in the 1/6 market where a production piece is better than the prototype and I'd never assume that to be the case; although I'd be lying if I said I didn't wish for that to happen with every figure. I think Hot Toys has been able to match production to prototype, but I think it's safe to say that production pieces will almost always be worse than prototypes simply because of the normal loss of sculpt detail involved in the manufacturing process (sculpting more detail on the original piece can partially mitigate this) and how much attention a prototype will get to generate the pre-orders (and licensor approval) versus the level of attention each figure gets in mass production.
Of course, stellar production paint can make up for loss of sculpt detail. Skilled painters really can work wonders. I've seen plenty of pictures of generic dolls painted to look almost lifelike, but who can afford to have every sculpt repainted by a master? And at today's prices, no repainting should be necessary.