Which one commits a greater sin: the fornicator, or he who looks at a naked woman's entire body and touches her limbs while she is asleep and unaware?

No, both the act of adultery (zina) and unlawful touching are forbidden and incur Allah's wrath. However, adultery (zina) is more heinous and grave due to the tremendous evils that result from it, such as the mixing of lineages and the loss of progeny. A Muslim is not permitted to choose between sins; rather, they must abandon all of them, as Allah Almighty says: "And abandon open sin and secret sin," and as the Prophet (peace and blessings of Allah be upon him) said: "And when I forbid you from something, then abandon it."