The Blueair Blue Signature and Coway Airmega 400 target different priorities in air purification, with the Blueair clearly dominating in raw performance and value. The Blueair boasts an extraordinary CADR for smoke of 2163.2 and can effectively clean rooms up to 3385 sq ft. This makes it an ideal choice for large, open-concept living areas or even light commercial spaces where rapid and extensive air turnover is critical. Its HEPASilent filtration technology efficiently captures 99.97% of particles down to 0.1 microns, combined with OdorFence technology for strong odor elimination. Furthermore, its unique design allows it to double as a side table, adding functional utility beyond just air purification, a practical touch often overlooked in appliance design. In contrast, the Coway Airmega 400, while still a capable purifier, covers a more modest 1560 sq ft with a smoke CADR of 328.0. Its primary distinction lies in its filtration precision and quiet operation. The Coway utilizes True HEPA filtration, capturing 99.999% of airborne particles as small as 0.01 microns, offering a slight edge in ultra-fine particle removal compared to the Blueair's 0.1 micron claim. Crucially, the Airmega 400 can operate at a remarkably quiet 22 dB minimum noise level, making it exceptionally well-suited for bedrooms, nurseries, or quiet office environments where noise is a major concern. The most significant differentiator remains the price-to-performance ratio. The Blueair, priced at $344.99, delivers over double the coverage and more than six times the smoke CADR of the Coway, which costs $638.65. This makes the Blueair an undeniable value proposition for those prioritizing sheer cleaning power for large spaces. While the Coway offers superior quietness and marginally finer filtration, these benefits come at a considerable premium and with reduced overall coverage capacity. Buyers must weigh whether the extreme quietness and ultra-fine particle capture of the Coway justify its significantly higher cost and smaller coverage area against the Blueair's unparalleled performance for its price point and added design utility.