GokaiChange appears to be a much clever option to pick during battle, since after you transformed into your desired Sentai senshi, you immediately possess all of their powers/abilities/weapons -- You GokaiChange into Dekaranger, and you gained access to their D-Magnums and other **** straightaway. You GokaiChange into Hurricanger, and you could execute their Chou Ninpou abilities in a flash.
Whereas in Decade, in order to make every single move, there was this hassle of needing to get a card into the Decadriver -- KamenRide~Kabuto. AttackRide~Clockup. FinalAttackRide~KaKaKabuto.
Can you imagine if the Gokaiger has to go through all these hassle (of one card/key for every move)?
*insert key* GokaiChange~ Magiranger!
*insert another key for an attack* GokaiAttack~ some Gii Magika~
*insert yet another key for trademark attack* FinalGokaiAttack~ another random Magika~
But... I'm still voting for a KamenRide, because... I love that ****!
Oh, and I also love the fact that the Decade Belt is still part of any Rider whom you transformed into.