......I use philips nighhawk bulbs.
Nighthawk is a GE brand. Philips top-of-the-line would be Xtreme Vision
FWIW, I've been running the LMC kit for about a year with no issues. Granted, my climate is a lot drier than others, so maybe that helps. I also mounted the relays with the connector facing down, plus they're mounted pretty high up (near the passenger battery), so that should keep the moisture out.
While I would LOVE to have HIDs in my truck (a legit setup, not just HID ballasts in the stock housing), I've been satisfied with the light output from the stock lenses, this kit, and a good set of bulbs. My lenses are in great shape, so that helps. When I first installed the kit, I installed a new set of GE Nighthawks. The light output was great, but one bulb burned out just last week. Not happy with that since I went with these over the Sylvania Silverstars specifically because the Silverstars are notorious for short life. I just installed a set of Philips Xtreme Visions last week. Can't say I see a huge difference between the GEs and these (too lazy to do a side-by-side. sorry), but again, not disappointed with the light output overall.
Given all the products on the market to clear up yellowed/foggy lenses and the relative cheap cost of a set of new lenses, there really isn't a good reason to be running around with poor light output on a bricknose. Yeah, 9004s are not the best bulb out there, but with the right set of bulbs, the relay kit, and clear lenses, it's fine.
Mike