According to
this article on the T-38s used as companion trainer to the B-2, the difference between the aircraft is exactly the point as they are used for exercising different parts of the pilots’ skill set. Interesting that they make the (few) ab-initios fly 2.5 years in the T-38 before even touching a B-2, which speaks to BV’s point.
Sims will increasingly be the best way to carry out tactical training; the primary gaps I can see are physiological (tolerance to ‘g’, airsickness and disorientation) and general airmanship. The latter could potentially be overcome if the synthetic environment was made more realistic in terms of things like ATC, other ‘random’ traffic, radio chatter, weather, etc - today’s sims are a rather sterile environment where the focus is very much on the exercise.