But following her second pro fight -- a third-round TKO against lightweight Jozette Cotton last weekend at PFL 6 in Atlantic City -- that comparison isn't as evident. If anything, there's now a stark difference between Harrison and Rousey to point out.
Two fights into her MMA career, Harrison has accumulated 14:42 of cage experience. It took Rousey 11 fights (amateur and pro), spanning more than three years, to log the same amount of time.
"Initially, I was disappointed, but I got over it pretty quick," said Harrison, on her sophomore MMA contest. "If I don't win in dominant fashion instantly, I'm not happy. But I talked to my coaches and my boyfriend [UFC welterweight Tony Martin] and realized I got a lot of good experience.
"In a way, Rousey was lucky her matches were so short because no one got to study her. But the fact she could always go straight for her opponent's head and get into the clinch, I feel it didn't help her development never being able to go three rounds. I won't ever say anything bad about Ronda, but every fighter has to adapt in MMA. It's constantly changing. Gaining that experience was really good for me."
As a two-time Olympic gold medalist in judo transitioning into MMA, Harrison expects the Rousey comparisons. Rousey was an Olympic bronze medalist in judo prior to becoming a UFC champion.
But as you listen to Harrison describe what she's been working on in the gym, you get the sense she has learned not only from Rousey's enormous success in MMA but also her limitations. The end of Rousey's career was defined by her inability to adapt to opponents who neutralized her judo.
"I say it almost every interview, but head movement is something judo players never think about, because no one is trying to punch you in the face," Harrison said. "Head movement is so key, and it doesn't come naturally to us. Slipping, rolling and parrying punches is huge in MMA.
"Of course I'm focusing on my striking, but also how to get into the clinch safely and effectively. And if I can't take them down up top, I can take them down below the knees with wrestling, which is something I never really did in judo."
Harrison, 28, intends to get right back in the gym following this latest win. Her PFL contract, which has two fights remaining, stipulates that she fights at least once every four months. Her manager, Ali Abdelaziz, has already publicly suggested a fight on Dec. 31, on network television.
She's been a professional fighter for only two months, but has already made it clear her eventual goal is to beat UFC featherweight champion Cris 'Cyborg' Justino.
Justino (20-1) has had an up-and-down relationship with the UFC for years, and has mentioned the possibility of exploring options outside of the organization when her contract is up. Regardless of promotion, Harrison says that fight will happen when she's ready.
"I would love it if Cris were to end her contract with the UFC [in 2019], and maybe she'll want to come fight in the PFL," Harrison said. "PFL takes good care of their fighters. They're into promoting their fighters. I think she would be treated much differently here and who's to say, maybe we could meet in the finals [of PFL's season format].
"I know that to be considered the best in the world, I have to beat Cris. I don't think I'm ready yet, but I know I will be. I'm not going to make guesses on the future, but I do know I will fight Cris Cyborg."