If you don't mind spending a little extra money I would actually get/make a 520nm. It's a bit more unique, still very bright, and easier on your eyes in the dark. But it's also a diode not DPSS, so it won't be affected by the cold as much whe you are outside... You can get up to and over 50mW pretty readily, and it'll have a good lifetime too.
Edit: if you're looking for being visibility it's not about total power, it's about concentration power. Laserglow's lasers have a thin beam, so the total intensity is higher, so the beam is easier to see than if we did the same thing with a typical g-lens because it has a larger diameter