The device characteristics and performance leverage of a SiGe epitaxial-base HBT are compared to those of an advanced Si double-poly ion implanted(I/I)-base BJT npn structure. In addition, a collector-base profile optimization for the SiGe device structure is described. Two dimensional numerical process and device simulators and a lumped equivalent circuit model generator are used for the comparison along with experimental data. The simulated results show greater than a 3x increase in current gain, a 1.5x increase in the unity-gain cutoff frequency (fT), and a 13% improvement in ECL circuit delay for the SiGe device. The experimental results confirm the device behavior predicted by the simulations.