I already posted this exact answer, but I'm on my phone.
Basically, McVay is an inside out leader who builds players up as well as teaching the details. This theme is encapsulated in Chris Cooley's comments.
Shanahan, otoh, is more of a "right way" guy that will drill and drill and drill until guys get it right.
I've literally found zero negative inputs from any of McVay's former or current players, coaches, or bosses. The same can't be said for Shanny. Moreover, Shanny specifically got dinged for his staff issues in Washington.
McVay strikes me as a MUCH better fit for how Goff seems to respond to coaching than Shanahan's method. Shanny has been openly hard on the veteran Ryan this year.
I don't want that for Goff.
McDaniel was like that...didn't work out well.