I use a 300mm Hiro as my main knife dail, coupled with a 150 petty in a pocket saya. I like the length because I always have enough blade to slice. Also, there is always a section of blade with an almost fresh edge on it because there is just so much blade to use. I like the extra width at the heel, just seems to make chopping veggies easier. The main disadvantage is it just being too long for some of the tight spaces, on the line in particular. It also is a bit over the top for brunoising shallots and similar fine tasks, this is where the 150 comes into play. I have 270 TKC and I find myself reaching for the 300 much more often than the 270.