Help me choose the best grafting knife, right know i have the draper 76777 (the first photo) but it is a single edged knife. I am between those grafting knives in the photos, if you recommend something else let me know! Also should i sharpen the blades of the knives? The knife will be mainly used to graft fruit trees like citrus. Is it worth to give $40 for the victorinox in the last photo?