The big difference is the age and how it translates to the position they play. RB's over the 30 year old mark typically lose a step and their play declines rapidly. A 6'6 265 TE may lose a step after hitting the 30 year mark but they typically will use their height and size and route running to get open.
I don't want to pay Bennett more, I just think cutting him or trading him leads to another need for the Bears.
I love Forte and would love to see him finish as a Bears, I just don't think it will happen with how good Langford and even Carey have looked this year.