Much like adults, I think kid's gear needs to fit the kids.... My daughter received a gifted a rectangular sleeping bag from a friend of mine whose kids had outgrown it. It was quickly replaced by a warmer mummy bag designed specifically for kids as we tend to head out in the winter more than the summer, and the gifted bag was very wide on my stick figure child. His kid loved the rectangular bag.... Mine, not so much.
9 times out of 10 I'll find a "kids" version of what I'm getting myself. Example, REI's wool pants has a kids version... hers are blue mine black. We usually share a tent (Big Agnes Scout UL), we both carry REI backpacks (hers much smaller obviously). We both use Camelbak's (mine 3L, hers.... 1.5L I think?)... And so on. Where I can't find an exact match ( I wear Vasque boots, and she wears Merrell's) I usually pick them out using the same criteria.
Sorry, not an exact answer to your question, but hopefully helpful none-the-less.
