After a long search I decided on the 75i because of the large space it covers, we have a great room approximately 1,000 square feet. With the 60 day guarantee I thought why not try it. Easy to set up, works great. Always looking at the color to check air quality, goes to orange when cooking, then back to blue. My allergies seem better, which is why I bought one. The best part is that it’s so quiet! I was worried about noise, that’s another reason I bought this model. Thinking about buying another one for our bedroom!