Christadelphianism is a relatively new religious system with less than 100,000 members. It claims, like many other non-Christian cults, to be the authentic Christian Church with authentic Christian doctrines. However, it denies the Trinity doctrine as well as the deity of Christ and the Holy Spirit. In addition, it states that the Devil is not a real person but is, instead, our natural tendency to sin. It also says that Jesus was a created being who had a fallen nature who himself needed to be redeemed. I say these things upfront as an introduction to Christadelphianism because we need to understand what the heart of this group is. Again, it is not Christian.
There are, however, disagreements within the camp of Christadelphianism. Several Christadelphians have pointed out to me that there are differences of opinion within their sect regarding the fallen nature of Christ. Nevertheless, they all deny the deity of Christ and this is enough to put them outside the camp of Christianity. A Jesus who is not divine cannot save anyone - especially one that needs to be redeemed himself.
In my opinion, Christadelphianism is a dangerous cult because it brings people to eternal damnation by teaching a false God and false gospel. It deviates from the central doctrines of the Christian faith sufficiently to make them non-Christian.
I would like to add that many years ago I had the opportunity to spend five months attending a Christadelphian Church during their midweek Bible studies. The people there were very warm and friendly. They freely allowed me to present the "opposing view" to their Bible study group on a regular basis. I was impressed by this. They also were very knowledgeable about scripture and listened intently to what I had to say. I found them to be polite and well studied and I enjoyed my time with them. However, they still denied the essential doctrines of the faith even when I "stumped" them in doctrinal matters. Though I remember them with fondness, I am saddened to know that they have chosen to deny the true and living God.