depends on what you're looking for. depends on what type of experience you like to have. anyway, i've grown k.o. the f2 version, but, i haven't grown jackberry. if, i had to choose i'd just get both. but, since i'm not choosing... i'd grab one and request the freebie that has the closest genetic heritage of the one i didn't get. k.o. is flame, knock out power for real, reminds me of bubba, earthy skuny, danky put your ass to sleep smoke. world class potency. i'd pick jackberry just for the flavor, but, i haven't yet because, so, many other strains i've grown from sannie have the blueberry thing going. my k.o.'s were short single cola type(untopped) plants, extra veg time helps on the yield(average), nute whores. put your best kush up and i'd put ko against it. DANK!