Hi! I am a Christadelphian and would be glad to answer any of your questions. From what I know, here are the differences between JWs and Christadelphians (perhaps you all can straighten me out if I don't understand all of the JW teachings).
1. We don't believe in a personal Satan, but, as been pointed out, it is the natural inclination to disobey God within us.
2. We all take part in the bread and wine each Sunday.
3. We do not believe that Jesus came back in 1914 (even in spirit) but that his return is yet future.
4. We take the 144,000 as figurative of the body of saints, not literal.
5. We do not believe that Jesus preexisted.
Again, as has been pointed out, there is a far greater agreement in our beliefs than disagreement. When you compare this small list versus the divergence in our common beliefs from mainstream Christianity, we certainly find ourselves in the same foxhole so to speak. Hope this helps!