Both guys are right at the top of the class in terms of statistics and post-season honors. Bell has led the NFL in rushing attempts, while making three Pro Bowls since entering the league in 2013. Brown has led the league in receptions, yards, and touchdowns at various times, with six Pro Bowl selections.
The only difference here is that Brown has been doing it for longer.
The fact that Brown has been doing it for longer works against him here. He’ll be 31 by the next season opener, while Bell just turned 27. History suggests that A.B. is nearing the tail end of his prime, with maybe another year or two of top end production before an inevitable decline.
Considering that Bell is four years younger and made himself a healthy scratch for all of 2018, it’s fair to assume that he has more left in the tank than his (ex)teammate.