Do you do 1p or 2p? For 1p, all of them are fantastic. I own SoS and KBT and combined they're incredible. Like you said, both have shields against, but unless your opponent is using both, one of them is going to go through. PCC is stunning, and IMO - better than the others for its air attack, that is very hard and very expensive to block.
But, it all depends if you do 1p or 2p. Get them all? xD
I say go for glowin cauldron. Fire is only blockable by that hat which is semi fragile.
GC is AMAZING. I love this weapon, how stupid I was to sell it.
And do you mean Pirate Captains Hat? It blocks only 5 icons of fire, it would be better to get Flaming Oven Gloves, they're like 1k and do the same
(or Faerie Tabard and smash KBT, or really Pirate Captains Hat and smash partly PCC)