The turns at the burner can make for a shorter engine for sure. The turn going into the compressor seems to help separate the air from ice/rain/fod. Almost never see fod damage in a PT6 on a King Air.
One big advantage of the air coupled power coupling is starting in cold weather. A Garret King Air (B100) has a second battery and the ability to put them in series for a 48 volt start in cold weather, the PT6 powered ones don't require it.