I've been a soccer referee for awhile and have had a lot of experience with whistles. Any Fox whistle is a great whistle. The lower pitch really saves the ears after hours of blowing. With a Fox 40 or Fox 40 mini after the first 1 or 2 really good blows my ears were ringing and after a day of refereeing I was almost deaf. With the Pearl you could go forever with little hearing impairment. I think the lower pitch of the pearl would allow you to signal for help and still hear a reply. The Pearl is also much more noticeable from a much greater distance IMO.
A few have disagreed with me and side I was backwards. So it might depend on the person listening.
This is just my 2 cents.