Cedar has a mellower tone than spruce, but that has the downside that you don't generally get the same attack out of it. If you want a mellow instrument for fingerpicking an accompaniment to your voice, cedar is good. If you want a lead instrument with more dynamics, spruce might be more your thing.

But more important than both of those is the instrument construction. A Taylor will sound like a Taylor and a Lowden like a Lowden, regardless of what they're made of. Wood selection is really just fine-tuning after you've already made a decision on the instrument maker you prefer. (Although "maker" can be a loose concept, given that many of them are imitating Martins for better or worse.)

Graham.