They are all cool. The amiibo have their own voice actors and they are special characters. No support sadly.
Ike- Divine Ragnell
Marth- Divine Falchion
Lucina- Parallel Falchion
Robin- Thoron
These are their own exclusive weapons and only then can use it. They also give you custom acessories. I will use them for sure. Ike is the one that I like the most and I like the others to, but Ike is my favorite.