One is a huge restaurant, seemingly without walls or windows, that opens onto the casino floor. The other is a warren of dark rooms, equally large, but tougher to find on the second floor of this behemoth of a hotel. Each is operated by a restaurant company with major stakes in the steak business. Neither plows any new ground with its concept or menu, but both will do just fine in figuring out how to separate tourists from their cash.

Nothing but a shiny railing separates the groovy design of Union Restaurant and Bar from the casino action (and the people-watching) at Aria, but the place is so big (240 seats) that you will feel as if you’re dining alone even if you’re sharing the space with a hundred other carnivores. UR&B is the newest offering from the Light Group—known for serving beef and interesting appetizers in hip surroundings.

The Light Group started as a nightclub company, but has since opened several satisfying steak emporiums (Fix, Stack and Brand), as well as Yellowtail, in several upscale hotels. Corporate Executive Chef Brian Massie is known for jazzing up everything from sliders to beanie weenies, and making mundane munchies sexy for the party-as-a-verb-crowd.

We’ve always found Massie’s food at his other joints to be fun—his pigs in a blanket and steak “hot rocks” at Stack are legendary—but our four starters here were disappointments. Neither of the two soups—the white clam “chowda” and roasted tomato—were conceived with subtlety in mind, and both were so thick you could stand a spoon in them. Both are just fine, though, if you like your food to (literally) stick to your ribs.

Equally disappointing was the “Union Signature Crispy Duck”—a small pile of semi-dry, shredded duck meat and skin, accompanied by ultra-thin Chinese pancakes, scallions and hoisin sauce for making your very own Peking-style duck. The small portion is $35 and will easily serve four as a starter, but the time and trouble of making your own food is not worth it when the end product is this tepid.

What the King Crab Scampi lacks in finesse it makes up for in bulk. Four huge chunks of crab-leg meat are placed atop individual crab-leg shells—each lined with cracker mush and topped with minced bacon braised in butter. Artful it is not, but $18 gets you plenty of bites of sweet crabmeat; it’s probably the best deal among the apps.

Things improve when you get to the main point of your meal. Our American Kobe flat-iron steak ($44) was perfectly cooked and full of the mineral-rich flavor an expensive steak should have. The dry-aged, bone-in filet ($48) was a baseball-sized hunk of tender beef and about as good as a filet can get.

Of the two sauces tried, the classic Bordelaise was deeply imbued with beef demi-glaze and red wine flavors and chunks of intense marrow floating throughout the sauce, but the Béarnaise tasted of hollandaise—which is to say it needed more tarragon.

For dessert, nothing is too fancy, but they do justice to staples like Key lime pie, warm Mexican churros, apple pie (with a fabulous maple pecan ice cream), and five “pudding pops” of fine frozen flavors (milk chocolate, butterscotch, vanilla, peanut butter and banana).

Since things steadily improved during our meal, and ended on those dessert high notes, we left with smiles on our faces. Had the appetizers been stronger, Union Restaurant and Bar might crack the Light Group’s top tier. As it is, it’s probably doing exactly what its lease with Aria is telling it to—give the post-baby-boom generation a steak place in which to see and be scene.

Upstairs, its competitor, the Jean Georges Steakhouse, is playing for higher stakes. Not only has this vaunted Alsatian-American chef (Jean-Georges Vongerichten) already dazzled Las Vegas with one of its biggest culinary hits—Prime—he’s also revered the world over as chef’s chef. When he opened Prime 11 years ago, it was one of his first forays outside New York. Vongerichten has since expanded his empire the world over, and this place is now just another link in his chain.

It’s a shame that a chef of Vongerichten’s reputation doesn’t bother dry-aging at least some of his steaks (like they do at Union and at other premium steakhouses like Cut, Carnevino, Nero’s, Delmonico and Craftsteak). That being said, the wet-aged, bone-in rib eye (18 oz., $50) was charred to a fare-thee-well, and was mighty tasty, but it lacked the dense, complex minerality a true steak connoisseur expects.

Highlighting the steak were three splendid sauces—whipped Béarnaise, soy-miso and hot mustard—that were more complex and finely tuned than those at Union. (At Union, the sauces are $5 each; here there’s no charge.) After years of eating his food at Prime, we’ve decided Chef de Cuisine Robert Moore doesn’t know how to make a second-rate sauce.

Even more stunning than the steak was the Chilean sea bass under a miso-yuzu glaze that set off the sweetness of this swimmer swimmingly. Lovers of that old warhorse tuna tartare will find this version more than acceptable—mixed with puffed rice and avocado, seasoned with some real kick and bathed in a soy-ginger dressing.

We weren’t as keen on the side of a Comte cheese “fritter,” showered with shavings of black truffle that brought nothing to the party. Its price tag alone ($12) alerts you that the truffles used are hardly of the best quality.

For dessert, we only ordered one: the molten chocolate cake, to see if Vongerichten is still on his game when it comes to one of his iconic creations. He is, and you can pretty much consider this the definitive version of this time-worn treasure.

For years we’ve said every restaurant in Las Vegas would be a steakhouse if it could. Mr. and Mrs. Dubuque still get excited about big slabs o’ beef, Chilean sea bass, crab legs, iceberg-lettuce salads, fried calamari, shrimp cocktails and tuna tartares, but to the foodie world, these tired formulas are the culinary equivalents of General Motors—wheezing and puffing their way to gastronomic bankruptcy while their acolytes remain oblivious to the food revolution around them.

We expected more from two restaurateurs known for playful innovation, and razor sharp concepts. What we got was the same-old, same-old, in updated surroundings. The Dubuques will no doubt eat this stuff up. Both restaurants should be big successes.