Connecting digital information with the physical is one of the essential ideas of tangible user interfaces. The design of the physical representation is important especially for specialised domains like surgery planning, because surgeons rely heavily on their tactile senses. Therefore, this research work investigates the effect of a soft and a hard 3D model as an interaction device for virtual reality surgical planning. A user study with 13 surgeons reveals a clear preference for the softer, more realistic material and a significantly higher haptic user experience for the soft model compared to the hard one. These results advocate for stressing material aspects along with the interaction design in domains with an inherently high focus on tactile aspects.