I know that quite a bit of engineering went into the IKV Fusion carto. They're made to IKV specs. For instance, the filler is less dense than standard and the center tube fabric is MORE dense than the norm. This seems to make them wick nicely and I think it makes them last longer. I tend to get about three more days of good use out of them than I do from the Boges (2nd best IMO). They taste cleaner to me too.
I'm not sure if the coil wire is different or not but I get a noticeable amount more vapor from the IKV fusions than I do the Boge cartos.
The ones Max linked to are about $0.20 cheaper though. If I could buy one I might try them but I think it might be like my try with the Smoktech DCs. Try two and give three away.