I came across this thread since I'm looking to upgrade from halogen on my 2016 GC and I saw that no one posted anything helpful so I decided to some research for the greater good of the community.
First and foremost, the type of headlight on your truck is of utmost importance which is in line with @raminan's comment.
Apparently, LED's work very well in reflector assemblies but not so well in projectors. HID's on the other hand, work well in both reflectors and projectors. Interestingly, some headlights can be hybrids - projector for the low beam and reflector for the high beam - in which case you can mix and match LED's and HID's based on the type. (source)
From my findings, up until the 4th generation (1993 - 2010), all GC's had reflectors for both low and high beams, although it may be possible that some higher-end 3rd gen models had some projectors (not 100% sure on this one). 4th gen models are definitely equipped with projectors for at least one beam so you definitely want to avoid LED's for any beam sporting projector lenses (this applies to you @glhamden for your 2020 model).
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As for bulb suggestions, my research was focused on studying several review sites. Almost all of them ranked Cougar, Hikari and XenonPro as the best bulbs for LED while an overwhelming majority ranked XenonPro as number one for HID's.
Although Cougar and Hikari are more competitively priced, their 1-year warranty kind of turned me off compared to XenonPro's lifetime warranty. I personally rather pay a premium for piece of mind.
I will touch upon an important topic of choosing LED headlights bulbs. It used to be very simple, I bought it, put it on, went. And now it has turned into roulette. All these problems arise from the lack of certification. The Chinese and Koreans are trying to make a good LED light source for headlights, but in terms of performance and safety requirements, they have not reached the level of halogen. Yep, this is not your choice of free paper writing service, where you can point your finger at the first service that comes across.
I was wondering about this myself. I know that when I had my '15 Silverado, reflectors (which I had) performed poorly with LEDs, but the projector lamps (which came on the higher end models) were great with them. Not sure what I want to do with my WK2, but I do love the LEDs on my '19 Mustang.
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