Not only is it very similar but, unlike Chrome or Safari, every aspect of it is customizable so you can make it look however you want. Out of the box you can rearrange the the UI elements to match Chrome or Safari.
I absolutely hate the FF UI. I WANT to use FF, I actually switched a few months ago and did it for a couple of months. I THINK my problem (I say think because I feel like someone will measure the pixel and say I'm wrong) is that it feels like there is a ton of wasted space between the tabs, above the tabs. etc. I can't control the size of the top bars and they're huge compared to chrome. I'm a fan of tiny icons and very, very compact UIs so that I can get more on the screen at once. Here's my comparison on a 28" monitor https://www.dropbox.com/s/k32gln7s3ev5a7t/Screenshot%202016-...
You might try the "Custom Tab Width" add-on to shrink your Firefox tabs. I also like to set my toolbar bookmarks' names to an empty string, so my toolbar is just a bunch of bookmark favicons.
Not only is it very similar but, unlike Chrome or Safari, every aspect of it is customizable so you can make it look however you want. Out of the box you can rearrange the the UI elements to match Chrome or Safari.