Shadrock,
Aside from selecting a manufacturer for insulated doors, you might want to consider other factors as well. Often, high quality expensive insulated doors are less than optimally effective because of poor installation. The rough opening size needs to be exactly what the manufacturer recommends or it will be difficult to properly weatherstrip the door. Also, the weatherstripping should be top quality and installed with no gaps where winter winds or blowing snow can enter. After the stripping is in place, the edge against the opening should be caulked to prevent infiltration. Plus, the weather stripping should be butted snugly to the outside concrete apron so air does not enter under the bottom of the stripping. If the concrete floor is not flat at the door or there is a crown or dip at that point, the standard door bottom seal may not be thick or flexible enough to remedy that problem. Most manufacturers have extra thick and pliable bottom seals to address this condition.
Just some thoughts to get the best performance out of your expensive insulated doors.
Glen