Dreamwear full face mask Medium or Large?

I have been trying both sizes and am struggling to figure out which is best to use. According to their sizing device I am definitely a Medium (I'm almost a Small even). When I wear the Large however I find that I can breath a bit better through my nose. It's subtle but I think it's there. I'm wondering if I'm experiencing placebo effect since to me the nostril openings on both masks look identical in length and width. I would just stick with the Large but the manual clearly states for best results use the smallest mask possible. I'm wondering why this is? Any advice on what I should use?

According to their sizing chart my ginormous face needed a small. I tried both the small and the medium, and neither would seal against my face. Never even tried the large because the chart said it would be way too large for me. Thank goodness for return insurance.

Use which ever is the most comfortable and allows you to sleep. Size recommendations are strictly that. Nothing says you cannot use a different size if it helps with your therapy.

Thanks guys. What do you make of the line in the manual that says using the smallest mask possible will be most effective. Is this them guessing that the smallest will seal better or does the extra volume inside the large mask take away from the treatment?

You should use whichever size works best for you. I would guess that the recommendation in the manual is there because most people don't like a lot of extra cushion hanging off the end of their noses. There is a lot of overlap between the sizes of the DreamWear Full Face cushions. I've tried the small, medium, and large (and they all worked fine).