This study offers a comparative study on various nano-carbon reinforcements differing in their dimensionality (D): carbon nanotubes (CNTs) and graphene nanoribbons (1D), Graphene Nano platelets (GNPs) (2D) and Graphite (3D). A wide range of composite characteristics were investigated including mechanical, electrical and rheological properties. We found that the optimal nanomaterial concentration (ONC) yielding a maximal reinforcement is typically located in close proximity to the rheological percolation threshold, in which an abrupt increase in polymer matrix viscosity is found. Therefore, such increase may be utilized as an indicator for the ONC. The 1D filler, i.e., CNT, is more effective than fillers of higher dimensionality: it yields optimal reinforcement and percolates at lower filler loading. In terms of processability, the GNPs are advantageous in dispersion and demonstrate milder rheological effect. Moreover, the GNP offers valuable reinforcement in a wider range of filler loading. To provide a facile comparison, a figure of merit is introduced taking into account the essential aspects of composite performance including rheological effect, enhancement, and loading (including range). Based on the figure of merit values, we were able to manufacture a robust hybrid nanocomposite utilizing the virtues of both 1D and 2D nano-carbon fillers. References: 1. Roey Nadiv, Michael Shtein, Matat Buzaglo, Sivan Peretz-Damari, Anton Kovalchuk, Tuo Wang, James M. Tour and Oren Regev. Carbon, 2016/ 99: 444-50 2. Michael Shtein, Roey Nadiv, Noa Lachman, H. Daniel Wagner and Oren Regev. Composites Science and Technology, 2013. 87(0): 157-163. 3. Roey Nadiv, Michael Shtein, Alva Peled, Gleb Vasilyev, Eyal Zussman and Oren Regev. Composites Science and Technology, 2016, 133, 192-199.