Definitely the biggest Macy's I've ever been in! The selection is outstanding, and - if you know where to look - you can really get a good deal. I was looking for a formal dress, and I'm a size 2; when I didn't find anything in the ladies' formal dress section, I searched out the Juniors department and found a dress that looked incredible on me for less than $70. (Perks of being small - and it's prom dress season, yay!) All the workers I interacted with were friendly; one of the Gucci workers actually helped point me in the right direction when I was disoriented (it's a big store!), and we joked a little. Overall, it was a very pleasant experience.
And in terms of Macy's in Las Vegas, this is definitely the best one. Next time I go to Macy's, it'll be this one. The underground parking is a little disorienting if you've never been before, but park near an escalator (they're color-coded - very handy!), and you'll be a-okay.