The Radiantz LED lamps are much brighter than the Kuryakyn. I have the Radiantz, buddy has the Kuryakyn, mine will make his seem dim if bikes are side by side. Kuryakyn comes with a run/turn/brake unit that seems to fail regularly, they do warranty them with hardly any problems at all, but you have to change back to OEM while unit is being shipped etc. Radiantz uses Biketronics units to control the seperate functions which you can buy from Radiantz or Biketronics direct (or Custom Chrome at the HD shop).
I installed my Radiantz unit the same date as friends Kuryakyn, mine is still good, we have replaced the R/T/B unit twice on his, the taillamp unit once and the complete asm once when Kuryakyn could not figure out what part was actually failing.
The major difference though is how much more intense the Radiantz units are. They also just plug in like the Kuryakyn.
FYI