+1 to the Diode Dynamics SS3 Pro MAX! I actually have a brand new set for sale specific to the GMC Yukon:
I purchased these for my 2015 GMC Yukon XL Denali and since I no longer have that vehicle I no longer have a need for these fog lights. These are probably the brightest LED fog lights you can install on your vehicle. There are plenty of pictures throughout the forums of other owners with these...
www.tahoeyukonforum.com
I had previously installed OSRAM CBI bulbs in my '15 Yukon Denali XL. If you check out this thread here there are some comparison pictures in post #25 next to stock OEM HID bulbs:
Instead of doing a total projector replacement so I could go LED, I'm thinking that it might be easier to just replace what I have with a better bulb. Hopefully with some improvement from factory. I believe I have halogen bulbs (2018 Yukon Denali) but don't know exactly what I have and can...
www.tahoeyukonforum.com
I have OSRAM CBB D1S bulbs in my '13 Escalade ESV and honestly the CBB probably have the slightly brighter and same white type output, but from the front of the vehicle looking at the projector/bulb color they're a little more bluish; But the light output is still very white. It's odd. Take that with a grain of salt though because the HID projectors on the '13 Escalade (GMT 900) are leaps and bounds better than the HID projectors on the K2XX Yukon Denali's. The OEM HID projectors on the K2XX Denali's are just garbage.
The HID Ballasts that
@Doubeleive posted above are top notch; I've had great experience with Hylux ballasts on previous vehicle HID set ups. You're biggest challenge will be mounting them and harness connections. Because the stock D3S HID Ballasts are mounted to be integrated into the headlight housing and an aftermarket HID Ballast will not fit in the OEM location.
I have a brand new set of custom projector retrofit headlights that were never installed that I might be willing to part with. If you're interested PM me.