[Designincase]

Much easier to fix the dumbbell neck joints then the one way.
If the dumbbell actually does break you can swap parts or build a new one. With the swivel, the damage usually cracks the neck itself.

With the limbs, you can easily disassemble it but I have had any problems with it. It would be nice if they adopted a sort of sleeve so would could replace a faulty joint while keeping pinless.

Swapping the heads cold can be difficult. Swapping them hot is very easy.