Right now, I'd say the Bears are roughly the same. They've gained some athleticism but lost some experience, and perhaps the kicker is that Briggs is of course another year older and eventually everyone gets old. They've probably gained on the health side, but both of the guys they brought in had better years prior to 2012, but if they stay on the field the full year, they're better overall.
If they add in a LB from the first couple draft rounds, then I'll genuinely say they're strongly better on paper.
One thing worth noting...very few MLB's stay on the field in both running and passing situations. The Bears had one of those guys last year for 2/3 of the season. Even though he missed the last part, that's still an advantage, I think it gives more flexibility to a defense...so something may have to be done if the Bears want to do what most of the league does and rotate LB's.