Proper heat treating is more important than the type of steel used, though everyone has a preference in the steel area. I would make the kitchen knife out of 1095 or 1080/1084 if I had some handy. I've made several out of an old saw blade (L6?), and they have held up really well. I like to use steel as thin as 3/32" for paring and steak knives. If you're looking for a stainless steel, I'd go with 440c. For the chopper I'd use L6 if I were buying new steel, and might even use it at 1/4". If I was using recycled stuff, I'd get a leaf spring and forge it down.