I've changed my thinking on this, thanks to Kestrel, Bullseyebill, Thermal Guy and others on the subject...
Light output and characteristics of the M60 and M30 are roughly comparable.
The M30 must be run with a single cell, because it is limited on voltage input.
The M60 is more versatile, with a voltage input up to 9v.... it can run on a single cell, two cells, or even three primaries. And the nice thing about the M60 is that when the voltage drops below 3.8, the lamp goes direct drive (not cutting off your light, but gradually diminishing it... giving you a long runtime and warning that your cell will need replacing.)
I once was a believer that you needed two cells to drive an M60 properly and have changed that viewpoint. I now run both my M30s and my M60's off a single cell, my favorite being the 18650.
If I were you, I'd get the M60 for your application.