The out-of-state costs, the high cost of living in Boulder plus not being admitted into engineering would be major strikes against Boulder, for me.Yes, it’s a lovely town & campus. But it’s also a big school, with a history of a big party-school reputation, and with big-public-school drawbacks such as not-infrequent difficulty getting the classes you want/need.
If your son does end up at Boulder, however, he will get a good education in a beautiful setting, so much depends on your comfort level with the costs, especially vis-a-vis the much-less expensive ASU. Have you looked into ASU’s respected Barrett Honors College? Graduating from there may even out the academic reputation part of the equation.