There are pros and cons to each kind of installation.
I usually prefer a real can light with a separate trim. You just have a lot more options.
I just wired a house using Feit recessed lights similar to the ones in the link. They were not color selectable, just daylight. The homeowner wanted something that would not have a step baffle look. I have used those same can lights on numerous occasions, but I don't use them all the time.
For the outside, he wanted some RGB so he can change colors for the holidays. It's a three-story house and there are cans on the first level and wrapping around the third level. Same trims as above, but they connect with a Wi-Fi app to be able to change the colors.
We also put dimmers throughout the house before I realized fight also makes Wi-Fi compatible dimmers. I don't know if they work through the same app as the RGV trims oh, but that would be awesome if they did. However, we used Lutron dimmers and the homeowner does not know (at least yet) smart dimmers are available.
One significant advantage that a traditional can with retrofit trim offers is the variety of lumen output. Feit and other companies make trims that look exactly the same but having Lumen output options.
The ones looking like what's pictured in the link come in to different brightness has – 850 lumens and 1250 lumens. Anytime you have a stairwell or closet or pantry, or even the kitchen, it's nice to put in the brighter trims.
The canless lights are not downlights. They are edge-lit, so they light the space differently. For me, I see a clear advantage in using those if you have short ceilings. A down light will produce a lot of light spots on the floor, whereas The edge lit panels will like the space a lot more evenly. Additionally, they don't glare in your face so much when you walk under one.
The junction boxes are supposed to be mounted, and when I'm wearing a brand new house using them I always Mount the J box very close to where the light is going to be cut in later. But when adding them on a remodel, it's almost impossible to mount from underneath the drywall. I've never met anyone who mounts them in a remodel application.
For what it's worth, I have recently raised my price for using them in new construction applications. Because you have to lay out call the lighting so you know where to put the wires and then you have to lay out all the lighting again on the finish so you know where to cut the holes. It's either that, or use the flat metal pans so the drywaller can cut the holes for you. Either way, I just don't like them for new construction
