FMIC is better because you get the air flow directly into the IC. Downside is the IC is connected to the turbo and engine via a longer length of tube. The longer connection results in some pressure drop between the turbo and the engine's intake. FMIC is also prone to damage (impact or flying rocks) since it is positioned right in front of the vehicle.

TMIC uses a much shorter length of tubing to connect the turbo and the engine so the pressure drop is much less. Downside with TMIC is the IC requires an air scoop to keep air flow towards it. When the vehicle is not moving, the heat from the engine can "heat-soak" the TMIC which dramatically decreases it's performance until airflow is restored to lower it's temperature.