Durability has value. Lamb has not missed a game in his four-year career. His agent is certain to use that as a bargaining chip. His trajectory is going up (he's gotten better statwise every year), while it can be argued that with the injury, Jefferson's is going down.
I say give him $150 million to make him the highest-paid receiver on paper and use that as a bargaining chip to give him less guaranteed money. If they could get his guarantees to $100 million over four years, then the true value of his contract is $25 million per year because he'll never see the fourth-year base. Give him a $40 million signing bonus, possibly some roster bonuses and guarantee his base for three years. Then in Year 4, you can either renegotiate or cut him for a cap savings (but a dead cap hit, of course). That's the cost of doing business in today's NFL.