AutoCAD .NET :: Update DWG File From One Version To Another

I have written a basic web service using RealDWG(.NET) that can update a DWG-file from one version to another with an option to update an existing block attribute. No other content in the DWG file should be changed/corrupted/deleted in a way so it cannot be edited just as before my little service executed and saved the file. The service seems to work fine when using some sample files I have received. I've done a visual comparison using DWG TrueView 2013 and to my eye it looks the same. Any tool that could compare and list if something was changed or excluded from the original drawing?

I see that the file size actually differs quite a bit after saving the file. I expected that the file would be the same size when I specify that it should be saved using the same version as the original file (for example AC1021. I notice that a couple of fonts (SHX files) could not be found when reading the source DWG but I do not think that should have any effect?I see that several dbx files are being loaded when a file is loaded/parsed (AecBase.dbx, AecbElecBase.dbx, …). Do these object enablers require that I add any dependencies to my visual studio 2010 project? At the moment I only have a dependency to acdbmgd.dll. From the documentation I could not really work out if I needed to add more dependencies than the one I have but I might have been reading in the wrong places…
 
What program(s) were actually used to create the drawings I have tested but the service have to handle files produced with several different AutoCAD products (including different versions). Being new to RealDWG and most things related to AutoCAD.