By "trail" do you mean mountain bike trail or bike trail?

I have a Light and Motion Seca 1400. It's a great light for mountain biking. It's an atrociously terrible light for bike trail riding - the wide beam is blinding to oncoming bikers and pedestrians. I've had people yelling at me, clearing off the trail, etc. If your road riding with a group it's annoying to other riders as they get blinded if they look back - it doesn't really matter the power level, on low it's to low and on medium and high it's blinding.

However, if you're riding by yourself on roads it's ok. Still not great though, as it doesn't have as much throw as I would like. The beam also has a bit of a hotspot in front of the bike, reducing your ability to see around you and making you need more light.

I guess of those choices, the NiteRider looks the most promising, as it has a low power mode and both a narrow and wide beam - maybe at lower power it turns on the narrow beam more?

For road riding, I've been debating between the Ixon IQ Premium and the v2 Phillips Saferide -
http://www.bikeforums.net/commuting/...e-ranking.html

They have a shaped beam, so they don't blind oncoming bikers on bike trails, and not on bike trails they have an even beam pattern on the road (technically it's brighter at the top but the result is an even spread of light).

I've already written to much, I'd have to rewrite an entire essay, but basically bike lighting is weird. You double the light output, and your eye only perceives it as about 10% more light. Your eyeball also adjust to the brightest light it's looking at, if the light has a hotspot your eye adjusts to it and can't see as well. Also, the more light you throw out in general, the less you can see through peripheral vision (as your eye adjusts to the light output in front of you).

So far, the Phillips Saferide v2 has been the best light I've used for road riding, though that's partially because I haven't had a chance to ride on the road with the Ixon IQ Premium yet (took it out in the driveway, but not on a real ride yet). I own a 200l - it's better than that, better than 2 400L's, better than my Seca 1400 (imo) as it has longer throw and less negative affect on my night vision.

Only thing that's better is a combination of both my Seca 900 and Seca 1400, because it gives a better beam pattern - and then "better" is subjective as I'm putting out so much light I seem to be blinding oncoming cars.

Whatever, just try to order from some place that you can return to if you're not happy with it.