We can compare the last 2 seasons, in which both players had probably the most comparable group of offensive talent around them.
Allen:
2-2, 63% completion, 11 TD's (4.6%), 3 INT's (2%) 299 YPG, 90.0 passer rating
Mahomes:
7-0, 70% completion, 13 TD's (5.2%), 1 INT (0.4%) 279 YPG, 107.5 passer rating
Allen is a lot closer to a guy who had one incredible Mahomes plus playoff run than a guy who is actually consistently on his level.