He’s correct, mid sized SUV.The best deals in used cars are the 3 year old lease returns. Generally under 40K miles and about 1/3 to 1/2 off orig. sticker price.
Having driven about 1.25M miles in my career, I like the ride of a sedan but the convenience of a mid size SUV. Some of the newer small and mid size SUVs have a ride nearly as good as a sedan, and nearly as good of gas mileage. As for exact choices, that is a personal thing. Ask 100 people and get 98 different answers. But I will say that something to keep in mind is maintenance on the trip. A cross country trip will almost always need at least an oil change. Pick a make/model that will be able to be serviced along the way without those dreaded delays waiting for parts to come from who knows where.