I would go with the "I" with the two slashes. It's been used since the beginning on ixcoin.org. CEX.io uses it. It's already established so to prevent confusion I vote to keep using it.
http://ixcoin.org/That's a good argument but since nobody in this world seems to know about IXC this is the perfect time to change it if we're ever gonna do it.
What I like about X is that you can do so much with it and it seems everything about iXCoin revolves around an X. Like i
Xpay and I can imagine i
Xcard, iXcredit, iXloans...etc.
Also every iX wallet starts with an X.
And of course, all global currencies start with X so it would be quite telling if iXCoin then would adopt the X symbol, a symbol known and recognized by any and all languages on earth, even the illiterate who cannot read a single word.
This is why I suggested using the X.
But I like the i very much as well, just for different reasons so I am curious to see which one gets the most votes.