As I have only used ArchiCAD to any extent, I can personally only recommend ArchiCAD and so will most people on an ArchiCAD forum! But I suggest downloading the demo versions of both software, go through the help files, tutorials and guides for each and see what works best for you.
ArchiCAD demo see here -
https://trialregistration.graphisoft.com/
The Interactive Training Guides that take you through all the functions of the software are found here -
http://www.graphisoft.com/products/archicad/ac11/itg/
Also the reference guides are found in the 'Help' menu actually in ArchiCAD itself. (As well as a link to these forums!)
If you need further info or help, contact your local reseller directly, or ask on these forums. Plenty of helpful people on here who enjoy answering silly questions!
You will have to search out the equivalent versions for Revit for yourself!
Best of luck!