G Rap hands down and I like L.
Kool G Rap could tell strong and compelling stories while still showcasing his technical prowess whereas many Big L songs are just him doing punchline rap which is good but not comparable to G Rap. Plus, career wise, G Rap's prime was much longer whereas Big L will always be a "What If" situation and the The Big Picture was already sounding worse than Lifestyez as his 2nd album.
Hell, G Rap also rarely ever sounded washed or dated even as he got older. He's a true anomaly who still could kill a verse or a posse cut while pushing 60.