I agree with pretty much everything that’s been said. I think it’ll mostly come down to preference, but I’d also say go for the cards if you just want the bonuses.
I mostly collect the Amiibo for collecting’s sake. I like to look at them. And mostly buy Amiibo that are Zelda or Metroid related. An exception I’ve made has been for the two Bayonetta ones that came out for Smash, because I quite like the insanity that is the Bayonetta franchise.