The DRLs (without low beams) seem to always be brighter since when the low beams are on, the halos are put in a lower power mode. Still, what I have in are brighter than the stock ones in either mode.

Short answer, it is the same bulb and it will only be somewhat brighter when low beams are on.

EDIT>> http://www.xoutpost.com/591805-post35.html

__________________
'08 X5 3.0si - Alpine White / Saddle Brown interior
Specs: Sport Pkg, Premium Pkg, Tech Pkg, Comfort Access, Aero Kit, Style 433 staggered 20s on Conti DWS
Mods: Carbon 35 tint, LED angel eyes, GP Thunder 7500k fogs, H&R 20mm/25mm spacers, clear reflectors, gunsmoke-tinted taillights
Coded: Digital speedo, windows/sunroof/tailgate close via keyfob

X5 pics at Flickr