I think D'qwell Jackson is the best option for 2 reasons.
1. Cleveland runs a 4-3 defense which means D'qwell is the middle LB and has to make plays from sideline to sideline. Having 4 DL's in front of him will help keep blockers off him and enable him to flow to the play and chalk up many tackles. Now he may not have a whole lot of sacks recorded but I think he did get one or two in the first week.
2. Cleveland does not have nearly as good an offense as Pittsburg which will most likely translate into the defense being on the field much more and thus increase D'qwell's oppornitunities to make plays.
Timmons may have more sacks but D'qwell will have many more tackles. If you want consistency I would go with the one that is going to get you steady tackle stats each week.
Deacon nailed it.
Also, look at Jackson's numbers the season before his injury. I believe he was a top 5 LB, if not top 3 depending on your scoring. And out of the gate he looks to be right back to his prior form. IMO not only will he be more consistent but also brings the potential for more big days.