I think Vcarve could compare to Bobart but not Bobcad/cam. The difference is what it can do. Vcarve is designed for creating image carvings (like Bobart) or text but not for machining pockets, profiles, drilling, etc.
So it really counts on what you are looking for. If it is 3D engraving you need then check out BobArt to compare it to.
Sheetcan can do 2 1/2 D but not 3D milling. I would say it is closer to Bobcad 2007 level 2 but with less options but does include nesting. Again it is what you need.
Bobcad probably seems more difficult at first due to allthe options available.