Ahmmon is about a half a step faster, if he was a low-mid 4.4 kid, Mello is around low 4.5 ish.
They have a similar physical frame in terms of being more of a lean muscular build, but can definitely add more weight. Mello's lower body is much skinnier than Ahmmon's though.
Ahmmon was a long strider with more wiggle, Mello doesn't cut on a dime in the same capacity that Ahmmon could, not that he can't he just rarely has to.
Mello I think has better hands, he's a very consistent hands catcher, he plucks the ball out of the air & can make toufh contested catches with CB's draped all over him, Ahmmon was good at that too though, so that could be a push.
Mello is a polished route runner, his in & out release, his ability to stem routes & stack DB's, he routinely wins the leverage battle at the line of scrimmage & is surprisingly physical with hand fighting against aggressive CB's, he understands how to get depth & create separation with his upper body. A long angular style route runner that can make acrobatic catches & has quick feet. He's learned a lot of the tricks of the trade from his cousin Ocho Cinco in how to win vs Press man with his feet & his setups.
He's a very smart kid with an A+ work ethic, he's competitive & loves to battle, a juice guy in the locker room that'll get his teammates fired up in big moments.
He has potential to be an immediate impact guy like Ahmmon was, Idk if he'll be as productive right away as AR was because with this staff you know Seniority supersedes all & they'll probably be starting Wiggins next year lol, but he's definitely a kid that will work his tail off & if the opportunity is presented he'll play hard.