The Christadelphian rejection of a personal devil is often cited as the main difference between JWs and Christadelphians.
What I’ve found interesting is that some of the apparent similarities between JWs and Christadelphians are not as clear cut when you look at the details.
For example both JWs and Christadelphians refuse to vote in elections. But when you look at the explanations for that stance, then clear differences emerge. JWs are essentially disinterested when it comes to politics. Many JWs are uncomfortable if the subject is discussed at all, even if no particular political views are promoted. They don’t vote in elections because they believe that Jehovah does not approve of any political leaders in this system and therefore Christians should not be interested in politics. Christadelphians on the other hand believe that God actively manoeuvres events in the world including elections and rulers and political developments. The reason Christadelphians don’t vote is because they worry they may vote for the wrong person “against the will of God”, so they abstain and stand aside to allow God to work out his plan. Christadelphians even believe that God uses the weather in order to shape world events including elections. One Christadelphian told me he believes that God sent poor weather during the EU referendum in order to get a Brexit result. As zionists Christadelphians are also intensely interested in events in Israel/Palestine and how they relate to prophecy and God’s plan. JWs on the other hand tend to ignore the details of political events, preferring to see the whole shape of the news as evidence the system of things is getting worse leading up to Armageddon.
Christadelphians and JWs also reject the Trinity and do not believe that Jesus is almighty God. But once again that is pretty much where the similarities end. Christadelphians believe that Jesus came into existence as a human on earth and did not have a prehuman life as an angel. They do not believe that Jesus is the archangel Michael. While JWs and Christadelphians both oppose the Trinity as a false post-biblical teaching, JWs are closer (although not identical, as they point out) to Arianism whereas Christadelphians are Socinians.
One area where JWs and Christadelphians appear to be in simple agreement is over rejection of the immortal soul in favour of soul sleep and awaiting resurrection to a paradise earth. They both reject hell as a literal place of torment.
And another difference, of course, is over the divine name. Christadelphian hymns sometimes use the name Jehovah, and individual Christadelphians will use the name Jehovah or Yahweh, but not to the extent as JWs or as the unique name of God.