At only 12 months you would be safer going into a convertible seat that allows you to rear face longer. The Britax line will allow you to rear face to 33 pounds, and the new Diplomat and Advocate will allow you to go to 35 pounds rear facing.
There are many other car seats on the market that will allow you to keep your child rear facing longer as well. Since 2001, the American Academy of Pediatrics has been advising parents to keep their children rear facing as long as the seat will allow, due to the crash forces found in a frontal crash (the most common type). By keeping the child rear facing, the entire spine rides down the crash force in a crash, allowing better protection to the spinal cord. When turning your child at 12 months, the only part of the child unrestrained is the head. Thus, in a frontal crash, your child's body is restrained by the harness, but his or her head continues to move forward at whatever speed you were going just before the crash. As a result, a forward facing young child, with an undeveloped spinal struture for protection, is more likely to suffer spinal injuries which can not be repaired.
This is why it is so important to keep children rear facing as long as possible. For your particular situation, a rear facing convertible, regardless of brand, would be safer for your child. As long as the seat fits your child, fits your car and can be used correctly every time you use it, any convertible seat you choose should be fine.