Best wavelength for IR LEDs to be used with a hacked up IR camera?
EDIT:After seeing mikeselectricstuff's comment, I agree: buy both. Then upvote his comment.

Pick the 850nm one. As shown in the following image (from here), it is attenuated less than 950nm.



The green and blue portion of your camera's Bayer filter will attenuate the IR light considerably, making their channels noisy, so you may want to look into getting raw image data output such that it can be processed on your PC, rejecting those channels. The filter cannot be removed.

Be careful with your IR "flash bulb", or whatever it ends up being. Although we can't see it, it still hurts and damages eyes. Many animals/insects are more sensitive to and can even see IR.