For a helmet mounted illuminator I have Surefire M1's on some of my helmets, and Armasight IR850W's on others. For weapons mounting, you can get Surefire M952v's really reasonable on ebay. If you don't need more than 100 yards of range, its a good option due to the versatility. I run the 600v because it is just as bright, smoother, smaller, and lighter. The streamlight offerings are absolutely excellent for the money as well. In fact, I should have streamlights newest product in the next week or so to review here. They are doing a TLR with an IR illuminator and an IR laser at a reasonable cost. I like the ability to have multiple functions in one unit to save space and for simplicities sake. The T-20IR is another great weapons mounted illuminator and hangs with offerings that cost twice as much.
You really want both though. Helmet mounted and weapons mounted IR serve two completely different purposes. I don't use IR lum unless I have to. A lot of hunting trips I will go out and never turn on an illuminator. But, it's not always avoidable, and it has benefits other than just lighting up shadows/indoors/really dark environments. They can be useful to scan a field for eye shine (for detection purposes). Just don't be that idiot that shoots at a pair of unidentified eyes, or anything else you haven't personally 100% identified as something that needs to be shot, safely.
For helmet use, one of the things I like in an illuminator is the ability to adjust focus and power output. You don't want to use the same power output to look for something indoors as you would looking for something across a field. I want a helmet mounted illuminator to have a constant on activation that is intuitive.
I also like my weapons mounted illuminators to have momentary activation.
What ranges are you looking at shooting the yotes out to?