You can use BA Avios to book, but 50/100/150 each way is the price, so that's a horrible deal. Plus BA will charge you higher taxes and fees than AA by several hundred dollars. (Plus you'd have to pay another 4500 each way for LAS-LAX, while with AA miles that flight is included.) AA miles can be great values flying abroad, while Avios rarely are. If you want to maximize Avios, see here