I don't worry about the ARF thing as much although given that the choices are there, I would choose to build. In this case I couldn't find a scratch or kit option that would yield a plane I wanted. I looked at House of Balsa and their P-51 looks bad to me. This one looks very realistic and although I wish it were lighter, I think the reviews indicate it is a good flyer.
I am definitely "Old School" in that for most of my flying time (30 plus years) the only way to fly something or fix something was to build it.
I may take the lines off this one a develop plans for a 50-55" mustang that is built lighter with much lighter wing loading. I have the CAD tools at my disposal but I have done some airplane design in the past and it is a lot of work. That's why I look at people like Pat Tritle (Pats Custom Models) and I often wonder how many hours he spends on the computer.