I never noticed the Predator line before!
Here is what I would do, the Predator Pro is 4AA instead of 2AA, and the bulb is 4watts, instead of 2 watts.
But as you noticed, it is 8 vs 4.5 ounces.
First, see if there is a place where you can see both of them.
2nd, I would get the Predator pro, and use lithium batteries, for two reasons. ONE, the lithium AA batteries are like 2/3 lighter than alkline, and TWO, they are brighter, and will maintain maximum output for longer.
BUT they are expensive. Cheapest posted price is 8.99 for 4 at Office Depot.
Someone had a "strap" that wrapped around your handlebar to hold a regular flashlight.
What I would do, is get TWO Princeton Tec Surge's, and wrap that around your handle bar.
Do a search on BICYCLE in SUBJECT ONLY for ALL FORUMS, and there are 8 topics total regarding bike lights
Do the same search, but use BIKE and there are 28 topics.
Sorry I can't find that topic, but I know it is here somewhere!