I find that the combination of the two leads to a more High quality bud vs just HPS. Less over all yield but a far superior product. I have heat issues so I use the HPS at the 400w setting as opposed to 600w and the LED’s add the perfect amount of extra light without the heat. When combined with lower than 60 def F during the dark period the buds will start to show purple colors and turn white with trichomes.
the LEDs are some generic eBay $40 a piece but work well. If I was going to use just LED’s I’d def spend the money and buy some better quality but right now they’re just adding more to the overall light spectrum and it works well. Hope this helps