While I'm far from a Luddite, unless you're currently embroiled in a to-the-teeth lawsuit with your municipality over your micro-domicile, these seem gimmicky to me. I have a dumbbell set of the more conventional design, with screw-on caps (Weider style?) I have four plates each of 2.5, 5, 7.5, 10, 15, and 25, though the last are really too big for single-handed dumbells and are used mostly for barbells, free-swinging stuff, and inside my ruck.
Limiting my comparison to the smaller plates that add up to 50 lbs each, I'm still not looking at that much acreage taken up in my basement workout room, especially compared to the larger plates, weight bench, and barbell bar.