I have 2 daughters myself. The older one is a brute and the younger is kind of petite. My oldest was firing a .270 by that age, but I consider her an exception to the rule. I think I would go for the lower recoil. I think she would enjoy shooting it more and there isn't a ton of difference. I just bought a 350 legend for my 9 year old. 20% less recoil than a .243 and you can sling 150-180 grain. You might want to look into the 350 also.
