These restaurants are parts of larger chains. My experience is with their Las Vegas locations.
The Yardhouse: A great place to hang out but keep in mind that it tends to be very busy, even on weekdays. The food is good, there's over a hundred beers on tap, and the service is always friendly and excellent. I've tried a number of their appetizers and can recommend all of them. The lobster artichoke dip is a particular favourite because it's a dish that, in addition to being really good, is something you'd never make at home. I recommend going after 10PM Monday through Wednesday for the half price appetizer special. You can eat very well for very little money. The only real drawback of the Yardhouse is the bar. While it does have over a hundred beers on tap, they're often out of about 20 of them. And, because it's so busy and the bartenders are relatively few in number in relation to the size of the crowd, they quick pour every beer. While this is fine for lighter beers such as Stella or Sam Adams, it does a disservice to the heavier drinks. Guinness is acceptable when this happens, but you end up having to let the Rasputin Stout sit for a few minutes before it's drinkable. Again, I recommend Yardhouse for hanging out with people, but I would not recommend it as an after work, grab a beer before heading home, type of bar.
Grimaldi's Pizzaria: They say that they are the same as the famous Grimaldi's in New York. Visually, the pizza looks like a proper New York pizza. The mozzerella is sliced not shredded, and fresh basil is scattered on the pizza. The sauce is a little sweet but overall the pizza is good, definitely try a bite before dumping on the parmesan or chile flakes. However, it is a bit pricey. This is where the real question comes in. There is no denying this is a good pizza, whether it's worth the price is a different question. There's good, not quite as good but solidly good, pizza elsewhere in Vegas and in most cities. And usually, you'll spend about $10-$12 for one of these solidly good pizzas (personal size) and a soda. A personal pizza, with a couple toppings, no drink is over $16 at Grimaldi's. I don't think the pizza is better enough to justify the price differential. Again, good pizza, but there's no doubt you pay a premium for the Grimaldi's name.