I ate similar meals at McDonald's and Carl's Jr. and saw why one is the dominant burger chain

I stopped by a Carl's Jr. in LAX on a flight from Los Angeles to New York.

The interior was mostly dark grey with red accents and stark lighting. I felt like I was in "Battlestar Galactica."

The menu is full of intense names like "The Big Carl" and "Western Bacon Cheeseburger."

But Carl's Jr. was also one of the first fast-food chains to roll out a plant-based "meat" option nationwide.

Read more: Plant-based 'meat' is conquering fast food. Here's where you can get meat substitutes like the Beyond Burger and the Impossible Taco.

"We gotta have a sense of humor around here," my cashier told me.

My meal arrived shortly. I'd ordered a Famous Star combo with fries and a drink ($8.19).

The price is accurate to the LAX location of Carl's Jr. that I went to.

I started with my Famous Star burger, which was hot and heavy.

It wasn't as tall as In-n-Out's perky Double Double or as wide as Burger King's Whopper.

My first bite revealed that the burger was thick in all the wrong places.

It tasted like a milder version of a Whopper, and the beef was just kind of ... there. The vegetables were fine, but they didn't add much other than volume.

Sadly, the most dominant flavor was mayo and ketchup.

A diner can tell the difference between a burger that's actually juicy and one that's juiced up.

It was time for my favorite kind of break: a fry break.

And these fries were exactly what I was looking for: crispy outside, molten inside. Carl's Jr.'s fries hit the spot.

They tasted like a better version of Wendy's fries. There was no metallic aftertaste. They just tasted like fried potato.

These tasted how I wish In-N-Out's fries tasted.

This wasn't a bad burger. In fact, it was a pretty good burger.

But everything about it was just not as good as it could have been.

As far as burgers go, this one falls squarely into the "average" category. There wasn't anything wrong with it, per se, but there wasn't much that was good about it.

There just wasn't anything about the burger that would make me remember it and crave it later.

I found myself reaching for the fries more often than the burger. They were good fries.

But if someone asked me what makes Carl's Jr. food "Carl's Jr.", I'd be at a loss for descriptors. It's just ... fine.

After I returned to New York, I went to the McDonald's restaurant across the street from BI's Manhattan office.

Surprisingly, this McDonald's had a similar dystopic vibe to Carl's Jr.

It was decked out in the same dark grey and piercing red that made Carl's Jr. feel like a battleship from the future.

Whatever happened to the fun, cheery colors of fast-food days gone by?

I picked up my order when my number was called and headed upstairs with a brown bag full of goodies.

I'd ordered a Big Mac meal ($9.79), which comes with a medium side of fries and a drink.

The price is accurate to the New York City location of McDonald's that I went to.

It's even the namesake of the "Big Mac index," which measures the cost of living in various countries.

So what's so iconic about a pile of bun, beef, and special sauce?

In the end, not too much. The Big Mac doesn't taste like a real burger in the way the Famous Star does.

It feels a little too dry, a little too constructed for that. But it does taste memorable.

If you took a blind bite out of a burger, you'd be able to tell if it was a Big Mac.

Because even if it isn't the best burger in the world, it's certainly distinct.

The special mac sauce adds an addictively creamy tang, while the layers of dry bun and middling beef respectfully do their jobs.

McDonald's golden starches are the golden standard for many a fast-food fan.

They're the fries that made the world love fries, but personally, I think the world can do better.

When they're fresh, they are crispy, salty, and pretty tasty. But they always leave me feeling a little empty.

Unlike Carl's Jr.'s fries, these feel thin, flimsy, and ultimately unsatisfying.

So if Carl's Jr. makes a slightly better burger and a much better fry, why is it so far behind its biggest competitor?

After all, the Big Mac is no big deal.

What makes it the "Big Mac index" and not the "Famous Star index" if the Famous Star is a better burger?

In this case, it's not about which makes a better burger, but about which makes a better brand. And at brand-building, the golden arches beats out the smiling star.