I agree with you on putting in the
spreading seas, but anyone who wants to make a competitive deck should know that it's not going to be the most budget. This is the most competitive I could make a merfolk deck for $70. No,
spell pierce is not better than
mana leak because
mana leak targets any spell and with
spell pierce, you can sadly only target noncreature spells. What about that one green deck you always play against that gets out
Worldspine Wurm on turn four, you can't
spell pierce that.
Bident of Thassa is extraordinarily important for keeping your opponent open for attack in late game, especially when you don't get
spreading seas or
sea's claim during a game, this is also where
merfolk sovereign steps in with the unblockable. I appreciate your input, I do think I will be taking out two Islands. I made this deck for anyone on a budget, I am not, although I am buying cards right now to put together a merfolk deck, and I will comment on how it plays in real time.