Controllable yield strength of Magnetorheological (MR) suspensions makes them suitable brake material. MR-fluid and MR-grease are two commonly explored MR suspensions, and comparison between their performances is useful to decide their suitability in MR brake applications. The current paper presents such comparison. MR fluid and MR grease have been specially formulated. Ninety percent (weight percent) of Xanthan gum coated electrolytic iron powder has been used for synthesis of both MR suspensions. Two identical brake assemblies, one for MR-fluid and other for MR-grease have been developed. Experiments have been performed in the same operating conditions of speed and magnetic field for MR fluid brake and MR grease brake, and their performances of brake power output and amplification factor has been reported.