When comparing the Alen BreatheSmart 45i and the Blueair Blue Pure 211i Max, the Blueair often emerges as the more potent and value-driven choice for general air purification needs. The Blueair 211i Max boasts a superior CADR for smoke at 406.4, significantly higher than the Alen 45i's 253.33. This translates directly to faster and more effective air cleaning in real-world scenarios, particularly in larger or more polluted environments. Coupled with its greater effective coverage of 635 sq ft, compared to the Alen's 395.83 sq ft, the Blueair is better equipped to handle expansive living areas or multiple interconnected rooms. Both units claim to filter down to 0.1 microns, offering excellent particle removal. However, the Alen distinguishes itself with a dedicated 'HEPA Odor Filter,' explicitly designed to neutralize strong household odors, a specific benefit not as prominently featured by the Blueair's 'True HEPA' filter. This makes the Alen a specialist for odor issues, whereas the Blueair is a generalist power-performer. In terms of smart features and user experience, the Blueair 211i Max takes the lead with WiFi connectivity and real-time PM1, PM2.5, and PM10 air quality monitoring, offering a more comprehensive and interactive control experience via its app. The Alen 45i includes a SmartSensor for auto-adjustment but lacks the detailed data and remote control of the Blueair. While Alen touts 'ultra-quiet operation' and a 'pink noise' feature for sleep, the Blueair quantifies its minimum noise level at a very respectable 23 dB, ensuring a quiet environment without relying on an unquantified 'ultra-quiet' claim. Furthermore, the Blueair's Energy Star Most Efficient 2023 certification means lower running costs, an important consideration over the purifier's lifespan.