These serve fundamentally different purposes: the Graco EXTEND2FIT is a versatile 3-in-1 convertible for extended use from 4-100 lbs with 10 headrest positions and dual cup holders, while the Chicco KeyFit 35 Zip is an infant-only seat limited to 4-35 lbs and 32 inches with GREENGUARD Gold certification, anti-rebound bar, and UPF 50+ canopy. Graco wins for families seeking longevity across stag...