Haven't got or used a iK but have a few Kwazar's (acid, normal & alkali) and have found them to be more than capable for my needs as a hobbyist not a business and are still working perfectly several years on.
I go for the 2 litre ones as I found the 1.5 litre ones seemed to need more pumping. Maybe they can't hold the volume of air or maybe it's just my perception.
Hope that helps.
Andy.