OneFunGenesis
<- Runnin' on Empty
Why?
More options in D2S. More manufacturing means better QC (generally). More interchangeable and readily available.
I'd recommend high quality (ex. OSRAM/Philips/Others) 5000K (crystal white...hard to find) or 6000K (slight blue hint) based on my years of messing with kits on other cars. Going with the cheap ones you will get a lot of blue tint at 6000K. 8000K is very blue regardless of quality.
As far as the Genesis and replacement of the bulbs, I have not done it but looked into it and it does not appear the bumper needs to be removed but you will likely need to remove some parts near the light housings to get to the bulbs.
Looked in the manual to confirm which bulb they are in the 2015, and they are D1S.
That kinda sucks. I would still say do 5000k (I have them in my car and love them) from here: http://www.theretrofitsource.com/components/bulbs/morimoto-xb35-d1s-bulbs.html#.VaVloPlVhBc