In stationary natural gas engines, lean-burn combustion offers higher engine efficiencies with simultaneous compliance with emission regulations. A prominent problem that one encounters with lean operation is cyclic variations. Advanced ignition systems offer a potential solution as they suppress cylic variations in addition to extending the lean ignition limit. In this paper, the performance of three ignition systems ? conventional spark ignition (SI), single point laser ignition (LI) and pre-chamber equipped laser ignition (PCLI) - in a single-cylinder natural gas engine is presented. First, a thorough discussion regarding the efficacy of several metrics, in addition to COV_IMEP, in representing combustion instability is presented. This is followed by a discussion about the performance of the three ignition systems at a single operational condition, i.e., same excess-air ratio (?) and ignition timing (IT). Next, these metrics are compared at the most optimal operational points for each ignition system, i.e., at points where ? and IT are optimized to achieve highest efficiency. From these observations, it is noted that PCLI achieves highest increase in engine efficiency, ?? = 2.1% points, and outperforms the other two methods of ignition. In conclusion, a closer look reveals that the variation in Ignition Delay (COV_ID) was negligible, whereas that in combustion duration (COV_CD) was significantly lower by 2.2% points. However, the metrics COV_ID and COV_CD are not well correlated with COV_IMEP.