The EM 400 is just the big brother of the EM 200. They are very similar in design to look at but of course the EM 400 carries a much greater load. Not only can you compare the spec between the pages here - but just have a look at the counterweights. The EM 400 is capable of carrying much more than at present....and it might have to, sometime in the future. It is hard to get a good picture of the mount within the Obs...but the link to Takahashi Europe will show more if needed.
The complete user manual (For Temma 2M) is inserted below for anyone wishing to browse through it.

Click on any thumbnail to browse slightly larger images.
It is possible to scroll through the above manual.