My review of each of them:
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Original: N/A
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Plus: N/A
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Connexion: Sounds nice, but never had it soo.. N/A
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Connection V1: Like the games better than the rest.
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Connection V2: My favorite, overall better than the rest, shop, more characters, more games etc.
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Keitai: N/A
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Good luck,
mametchichic