I've had neither system but from what I've read here on this forum, the Jardine will give you extra power, the Zard, while it looks good and sounds good, might cost you some power, and some of the zards have had quality issues....like cracking. YMMV
Blueflash went through two of them as the bracket on top cracked and came away. Replaced no problem by the UK importer. I seem to remember that members said it didn't deliver any extra bhp, but cannot confirm that.