I don't think the Helix will sound different at all. I believe it's just a marketing thing. If you read the literature about the previous Alpha/Vx series, they stated that Shunyata used a Helix winding pattern in their cables/cords. So I think it's just a matter of Shunyata placing the word 'Helix' on the heat shrink. I don't think the design changed at all.
Of course many will dump their 'old' cords to get the 'new' ones with the word Helix on the heat shrink. That's what I'm waiting for. :-)
If it had been an actual design change, they would have added a V2 or changed the name, like they did with the King Cobra to the Anaconda. I have no iside info, this is just my opinion of the situation as a long time Shunyata follower.
Regards,
John