I am in the market for a midsize suv. Are the engines on the GMC, Buick models comparable to the Honda, NIssans, Hyundais, in total milage numbers before major repairs?

If you take care of the engines and change oil often the engines should last a long time. I would not put Hyundai on my list of considerations.

Engines don't care what name is (cast) on the outside! 4cyls wear faster then 6cyls which wear faster than V8s if all are designed the same and there NOT...Turbos kill engines faster than naturally aspirated designs. belts wear faster than chains, which wear faster than a gear driven design. Good design is good ...Bad design is bad. EPA restrictions and cost factors control the design of modern vehicles. Review some of the best engine designs then select the manufactures who offer them.