I am in a predominantly Yoshinkan dojo (my Sensei is 5th Dan Yoshinkan, but also 6th Dan, I think, in Aikikai).
One of the main differences I have been told by my senseis and sempai is that in the early stages Yoshinkan concentrates quite a lot on the Kihon Dhosa (sp?) - the fundamental movements.
These six movements were emphasised by Sensei Shioda as being the core of every technique within the Aikido he taught and as such they are the foundation upon which we beginners (5 months now for me!!) can build to get our bodies to react in the correct manner without conscious thought!! (Difficult at the start and boy does it make the legs hurt!!)
I am not sure about other differences between styles as I have little experience, and I am sure someone will tweak what I have posted above to clarify what I may have got confused!!
Hope this helps even just a little bit!!