It really makes a HUGE difference to have a basement with much larger windows, whether it's a Walkout or Lookout basement. A basement without large windows will always remind you it's a BASEMENT, while a basement with large windows will be more like another living room.
Personally, as long as Lookout basement has equally large windows (some Lookout basements have smaller windows), I cannot see too much advantage of Walkout basement over Lookout basement, unless the owner wants to use that basement for some special uses (separate living space for renters or relatives; use basement as an open workshop, etc.).