Little backstory to help you all choose, not very spoilerific, but might have some. If you have more interest refer to the Golden Sun Universe Wiki.
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Venus: earth power, party leaders. Good attack, good spells, good support. [Issac, Felix, Matthew and Himi]
Mars: fire power, used by characters that are better attacking anyways. Some good spells and supports but nothing that great. [Garet, Jenna, Tyrell and Eoleo]
Mercury: water power, normally used by healing characters. These characters have a hard time attacking. [Mia, Piers, Rief and Amiti]
Jupiter: wind power, good all around characters for attacking but best support moves. [Ivan, Sheba, Karis and Sveta]
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