2 Internal Specs
The new base model Air gained a 1.6GHz dual-core 8th gen Intel Core i5 processor and 8GB of RAM (no RAM upgrade is available).
The 12″ MacBook starts with a 1.2GHz dual-core Intel Core m3, and 8GB of RAM upgradable to 16GB. That makes the 12″ MacBook slower than the Air overall, but with upgradable space for RAM. Overall we’d take the better processor of the Air, but this is another situation where needs can vary.