I'm not sure that the Westminster Confession, by itself is an improvement over the 3FU, but I do think the Westminster Standards, together as one, are more thorough than the 3FU (especially when the Larger Catechism is considered).

I was raised on the 3FU and still have a very fond place for them, though I now reference the Westminster Standards more often.

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Seth Stark
Member, Communion Presbyterian Church (ARP), Irvine, CA
Biola University, Graduate Student, M.A. - Science and Religion
Seth's Blog