The 25-year-old, who appeared in Jake Pavelka's season of The Bachelor, will front the sixth season of the ABC romance reality show when it returns later this month.
Speaking to ET Online, host Harrison said: "She did a great job and she was a phenomenal Bachelorette.
"I hate to say it, because I have said it before, but it was one of our best seasons we have ever had. It is a phenomenal season from the storylines, to Ali, to the travel, to the guys."
He continued to say that Fedotowsky is "completely and utterly" different to previous Bachelorettes such as Jillian Harris, describing the two women as "polar opposites".
"Jillian was so confident in many things where Ali is insecure and vice versa," he explained. "Ali is a very independent, emotionally strong, and heart-on-her-sleeve. One thing about Ali is you never wonder what she is thinking... If she doesn't like somebody, you will know."
Harrison previously teased fans that Fedotowsky was "satisfied" with how the season ends and the choices that she makes.
The Bachelorette premieres May 24 at 9/8c on ABC.
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