Depends how you define "walking distance".
Many of the LAX hotels are within a reasonable distance of the terminals, but it isn't exactly "walk-able". Especially once you get to the Sepulveda Blvd/Century Blvd intersection. No footpath on World Way that isn't directly at the terminal, and the paths along Century Blvd are poor quality or non existent in parts. There is no path on the south side of Century Blvd past the airport side of Sepulveda Blvd, and segments of the path on the north side are blocked by the people mover construction.
Meanwhile, the airport hotels around SEA are within the same distance as the LAX hotels. The path along International Blvd are wide and well maintained and you aren't required to fight the traffic to access the terminal. You can go to the bridge over the airport access roads and enter the airport via the light rail station near the Hilton.