Are any digital refrigerant manifold w/ vacuum reading - trustworthy?
No. Unless it has a separate sensor like the YJ's.
The two biggest enemies to a micron gauge are positive pressure and oil. If you're using your manifold for anything other than an art piece - the internal micron sensor will be exposed to large amounts of oil and several hundred pounds of positive pressure per day.
I just can't see how any digital gauge with a built in micron gauge can stay clean (free of oil) and remain accurate.