Abbo

In my humble opinion, a mask..is a mask..is a mask. The one I use most at the moment I bought dirt cheap in Thailand: a local brand. If you're the kind of chap that likes to drive around in a taxi throwing money out the window you might go for a fancy mask but, well, they're just windows. There's no reason why a fancy mask should fit better than a cheap one: it just depends what shape your face is.

In most shops they are all out of their boxes hanging on the wall. Go through them all. Offer each one to your face, suck in through your nose and see if it sits there on your face. If it falls off, where was the air getting in: most likely it was your moustache. No drama there that soap, water and a blade won't fix. No point sucking your eyes out of their sockets and looking like Marty Feldman, though.

Most masks leak a little. As long as it's only a little I leave it there: sometimes it's useful to wash your windows with. If you're using so much dil that it makes a meaningful dent on your gas use you might be overdoing the mask clearing: you're trying to ease the water out of the mask, not shoot it into the asteroid belt. Sure, you'd use a bit less gas clearing it if you had a lower volume mask, though.