I own a v2 of the Phillips Saferide, and have been testing the battery life. Here's what I got, at indoor room temperature:
2700mah rechargeable AA's -
High: 1:53
Low: 3:12
Off: 3:55
"Low" is the point where the light starting dimming below the regular light output of low mode. You can also switch it back to high mode from low mode when it switches automatically, and probably get another half hour of runtime on high mode out of it if you want. (Haven't gotten to testing it yet).
If I was riding with a light in the cold, I would...use a dynamo, lol. But for AA batteries, the Eneloop Pro's are the highest capacity (2550mAh type, 2450mAh min) nimh batteries that I know of that specifically claim to have improved chemistry for working in the cold:
Amazon.com: Panasonic BK-3HCCA4BA eneloop pro AA High Capacity New Ni-MH Pre-Charged Rechargeable Batteries, 4 Pack: Electronics
I own a B&M Ixon Premium as well. The beam pattern is much better for making turns. And the battery life is much longer as well - it ran on high for 6.5 hours with the same 2700mah batteries. But I can't immediately recommend it over the Saferide. The Ixon Iq Premium uses an LED with a fairly strong purplish tint to it, and it doesn't appear quite as bright. It works ok, but I find myself preferring to use the Saferide instead so far because the light it throws out does a better job at illuminating stuff on the trail, and it's just warmer and feels nicer. Dunno. We'll see.
Regarding visibility, I don't think the shaped beams are actually any less visible than non shaped beams to cars, if they're mounted in the same place. So far I feel like if they see one solid beam, they see the other. If you want more visibility, the thing to do is to put a reasonable-light-output front flashing light on the bike. Human eyes see flashing lights much easier than solid lights.