Ok,

There are defence combos that are built like so:

AR: Circle Upper or Samurai Upper
WD: CWD: Defence Ring, or a heavier one
RC: Grip Sharp
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They are really good, but sometimes I see people dissing them, well why? They are great combos with great defence. Samurai Upper on Grip Sharp with a heavy WD equals: Beyblade with a lot of weight that blocks away a lot of attacks with upper attack.

Discuss the uses of this combo, and the stadiums it wouldn't do as good as in other ones.

Very simple reason- it may not have enough survival. Also, really strong attackers can take them out.

Personally, I prefer:

AR: Metal Ape
WD: 15g Circle Wide
RC: Grip Sharp

Spin rate is not the only way to counter upper attackers. A very smooth underside also helps.
You can also try free spinning CWD, like Free Survivor with 17g metal piece.

For spin rate based defencers... I find, one use is to prevent it from flying too far. That way, it can stay in and sustain against the attacker. When it hits the stadium again, it won't lose too much spin. Smaller stadiums are more dangerous for it.
I would also prefer a bit of attack, in case you have to use it against a survival type Bey. Grip Sharp... has some attack power. With AR like Metal Ape, Metal Spring, etc., it can sustain a decent spin rate to smash attack with,