Concentrate on the most important features, which in my case is the cockpit functionality and atmosphere. Then, if resources exist, it is a bonus with exterior fidelity as wingflex, aircraft services, cabin and interactive doors, though no requirement. I confess I get satisfaction while watching a replay sitting in the cabin while experience a turbulent landing, but I prefer if main resources are concentrated as I wrote above, and resource excess may be added for less important features as discussed above.