Got that one going. Please everybody, this is not a battle between Flex and Monster cables. Sorry to say, "Size does matter". It's about the ability of the cable used to carry the current needed to drive the loudspeakers with minimal loss. Nobody should use the Twinflex, usually 0.5 sqMM copper for any serious performance use. However any, I mean any, copper cable of sufficient diameter copper will be correct to use.
Same for other electrical uses, take twinplex and extend your 2KW heater and it'll have to carry 10 amps for which it's not designed. It may even burn up. It's all about resistance in the circuit. Use 1.5 to 2.5 mm or more and you'll have the best there is, probably better than some of those the Specialists will try to sell you. By all means use Hull or whoever but make sure of the actual copper diameter or cross section before you buy. Interestingly Silver is the best conductor known, even better then Gold, if you could get (afford) silver cable it would only have to be tiny in diameter because of its low resistance.
By the way resistance is directly proportional to the length of the cable used, so if you only a 1 metre run you could use a thin gauge copper but if it's 20 metres go for the big stuff.