First, the boring, gory details.
SUMMARY OF MAJOR LEAGUE BASEBALL PLAYERS ASSOCIATION MAJOR LEAGUE BASEBALL LABOR AGREEMENT
Highlights from MLB Trade Rumors
The new agreement is terrible for low revenue teams.
There are numerous restrictions on spending for amateur players (the draft, international free agents). Amateur players are one place where low revenue teams have a competitive advantage against large market teams.
Here's a list of how much teams spent on draft bonuses in 2011. You'll see teams like the Pirates, Royals, Rays at the top of the list.
Here's a list of international signing bonuses. Again, Pirates, A's, Twins, Astros at the top.
Obviously, high-revenue teams are going to have an advantage signing major league players. These players are also less risky. If you pay $10 million a year for Rafael Soriano you have a much better idea of what you're going to get out of him than if you give a $3 million bonus to a 16 year old kid from the Dominican.
High revenue teams don't need to take as many risks on amateur players because they can sign more stable major league players.
Low revenue teams aren't going to be signing the best players and have to take risks on players in the draft and international free agents. Spending $2 million on a player that might bust or might turn into Miguel Cabrera is their most efficient way to acquire star players.
The new CBA limits their ability to do that.