Well there are situations in which you need to relax a joint to get what you want. Especially in multiplayer. In some occasions you want to extend a joint first and then contract it. This is rather used in indirect movements though. For instance relaxing a hip and contracting the knee. In the right situation the hip will stay the same while the knee contracts and then snap into its extend position (mostly used in air when you want to get the hip down) Good for getting a contracted knee behind you in aikido. Or relaxing a pec and contracting the elbow.

Speed is relax, and i think that force is for stiff

Relax is unpridictable, but stiff is harder to knock down...

In reality relax is not any more "unpredictable".

You can be stiff as a boner and still deceive your opponent better than if you were flopping around like a boiled noodle.

Unpredictability and deception is a trait of a good player, and is completely independent from what joint states they use more.

Look at how Nighend plays, his hold style kicks some serious ass. It doesn't look very fluid but jesus he can get some power.

I use relaxed alot. Its easier to dodge.

You know how your joints work before trying to relax IMO. In sambo, a simple noob clap can push you out. Though I don't use hold sometimes, i just contract,extend and relax.

Is better relaxed moves, cuz they're better to move, i mean faster.

Relax makes you look more "pro" in noob's eyes.
I mean, all noobs will be like "omg he is relaxed, it's so pro".

yeah u re right, it happened to me(when i was a noob ЌЌ)

All noobs will be like "omg how does he do that! i move so fast and weak and he moves stably and strong!"