Google Maps and Google Earth share the same image base however Google Earth, and now version 4, allows far more manipulation, larger view, more overlays, ability to tip etc.
As for image resolution this is changing all the time with more hires all over the world. In UK, a month of two back, Menwith Hill and Fylingdales were in lowres with the former not even visible. Now they are both hires with cars in car parks etc. GCHQ is interesting too are more than half the site is a construction site.
I use Google Earth in preference every time.