As I'm sure a few of your girlfriends have said to you in the past, size doesn't matter
Brooking sucks at the point of attack, and it doesn't matter if he is 245 or 270 pounds, if he can't take on blocks, he's not going to last in the middle. Our DTs aren't the type that are like Sam Adams/Siragusa that are going to eat up 3-4 blockers at a time. FBs and TEs and Cs have had free shots at Hartwell all year long, and its been a major contributor to why our run defense has struggled.
Among the "good" linebackers in the league, Brooking is probably one of the worst when it comes to taking on and shedding blockers. That's why he was moved to WLB, because at that position he is allowed to chase the football, and IMO Brooking only contributes to this defense when allowed to chase.
Reese is much better at the point of attack, and can actually shed blocks. Reese may not be as big as Brooking, but he's just as strong if not stronger. The question I have is if Ike is durable enough to start 11 games at MLB. THat's the only time actual size becomes a factor. But then again, Demorrio Williams is one of our smallest LBs and he has no problems whatsoever.
Brooking is totally neutralized when he's not allowed to chase the football, thus all the criticism he garnered when he played MLB and ILB for 3 years (2001-03) here.
Hartwell was the one guy at LB that would really hurt if we lost him. WIthout Beck backing him up, we lack a true MLB. But I think with the players we have left, Reese is our best option. He's not perfect, but in terms of what we want our MLBs to do, I think he's a better fit than Brooking.