Its really up to you, and which keyboard you think looks better, whether you'd rather a numpad, etc. etc.
Of the two you mentioned, based on sheer potential, I personally would get the BlackWidow. I'd have to sand the housing back and paint it, though. Partly for fun, but mostly because the shiny finish on the original housing would drive my psuedo-OCD wild. I'd be wearing gloves while typing to avoid fingerprints.
Someone else on here is probably in a better position to comment on the BlackWidow build quality, but I don't think theres much reason, if any, to expect that it will be anything less than acceptable.
Based on the keyboards as they are, I'd go QuickFire. If I was going to buy a QuickFire, I'd probably get the MX Red one with the different coloured housing, too.