Stormtide Leviathan makes all your opponents lands into islands, but its hard to cast and you really only need one island in play anyway, but Harbinger of the Seas almost certainly has several lands it'll affect and get you walking on time
For more on how this works, check out our general review of Star Wars Unlimited , which goes deeper into the mechanics of how the game is played
Mainly this is because now theres only 100 of each card, which is going to put a real strain on the whales of collecting, the type who have to have a full set of one of each serialized card
Paying four mana for your opponent's Blightsteel Colossus is good enough, but you're going to be hard to beat if you combine it with a flying creature or one that can't be blocked
With the absurd prices of official Pokemon cartridges, I would be aware of that risk at all time
Although the two rules are similar, the "legend rule" and the "Planeswalker uniqueness rule" affect different kinds of permanents