I'm not here to rain on any parades. I'd been planning to use an AiO for my Skylake project -- more likely a "customizable" AiO like the Predator 240 or H240 X2.
I fiddled with my case for a few months so there were options for either a 240mm or 280mm radiator assembly.
Then it was time to order parts. I wanted to look again at reviews comparing AiO and other coolers -- a mix of water and heatpipes.
What I discovered was that the LG Macho by Thermalright falls short of the EKWB under a certain test-bed loading by 5C. It beats the D15 by at most a couple Celsius degrees.
I had my 6700K delidded and re-lidded with Liquid Ultra for a 12C improvement in temperatures. With the Macho, it trumps the EKWB Predator 240 by about 7C.
The cooler seems more compact than the D15 -- significantly. it doesn't hang over the RAM modules. And for using a Noctua iPPC 3000 120mm fan for exhaust ducted to the rear of the cooler, with four 140mm intake fans and a CM Crossflow barrel fan as auxiliary exhaust, the system is terribly quiet.
Of course, all the fans are totally isolated from contact with case-metal or any other hard surface that would amplify motor-noise.
Since the OP mentioned the D15, I only offer this as a possibility that is "not for everyone." But figure I paid $50 for the CLU-relid, about $70 for the cooler and $8 for the accordion duct accessory -- less than $130. That beats spending ~ $180-something on a Predator 240 to run 7C hotter. Of course, you could buy an AiO AND have the CPU re-lidded to get the best result -- with a total outlay of ~ $230.
Put together an assessment of option risks, considering things like eventual pump-failure, leaks, etc. -- the choice is still a matter of personal preference. I just think it's a lot simpler.