The short version
Both budget True HEPA. Coway AP-1512HH is the Wirecutter-favorite with sensor + larger coverage at $229. Levoit Core 300 is the $99 bedroom-scale entry.
When Coway Airmega AP-1512HH is the right pick
If you want sensor + auto mode + Wirecutter brand-trust + larger coverage at budget price — Coway is the right shape at $229.
When Levoit Core 300 is the right pick
If you want cheapest credible entry to single bedroom — Levoit Core 300 at $99 is the right shape. Accept no sensor + bedroom-scale coverage.