The verdict: Flashy to the point of gaudiness, expensive but flimsy-feeling, big outside but not inside, Lexus’ flagship SUV drives well but is disappointing overall. Versus the competition: Competitors from BMW, Land Rover and Mercedes-Benz are more luxurious and higher-tech, while Cadillac, Jeep and Lincoln offer SUVs that are more reserved in their styling and more comfortable in their spacious cabins. Let’s face it: Big, full-size sedans meant to showcase the best the brand offers are no longer the flagships of any of the world’s top luxury marques. That distinction has been passed to the full-size SUV, a more popular — and usually more expensive — choice than a traditional sedan. It’s understandable; big SUVs are generally roomier, with the…