I have tested a few mini-mini cables I had around the house and some were definitely more prone to RFI/EMI noise. I even dissected some...there can definitely be big differences.
I picked out a cable that would work for portable situation(flexible enough, not too long), and had good shielding.
My JMT CHA47 works wonders in testing cables among other things...hook it up to a source with no input, max the volume (the JMT amp is utterly hissless). I can literally wrap my hand around the mini-mini cables and HEAR EMI/RFI noise easily on poorly shielded cables.
I had like 5 different mini-mini cables, 3 weren't well shielded but 2 were. On the otherhand 1 of them that was well shielded was a cheap radioshack.
But I don't use the radioshack because I found a much thinner cable that worked just as well if not better...and it had a few printed specs on it that I popped into google and actually found the specs and build of it on the internet. http://www.ltkcable.com/LTK_p_2547.htm