Using previously developed model for CNT density variation in CNFETs and random dopant fluctuation model in MOSFET, we compared and presented overall device variations in MOSFET and CNFET for gigascale integrated systems. Even if all of the sources of variation can be well-controlled in the manufacturing process, it is very hard (if not impractical) to control the dopant fluctuation in MOSFET and CNT density variation in CNFET device technology. Our analysis shows that in 32nm technology node, the random dopant fluctuation in a typical MOSFET creates 6.7% on-current, 1.1% off-current, 23% input capacitance, and 1.6% threshold voltage variations, while the CNT density variation in a typical CNFET with 10 CNTs in the channel creates 23% on-current, 22% off-current, 23% gate capacitance and only 0.011% threshold voltage variations. Based on our analysis, although the threshold voltage variation in CNFET is very small, the overall variations in CNFETs are worse than the variations in MOSFETs. As a result CNT density variation in CNFETs must be carefully taken into account for current gigascale and future terascale integrated systems.