Hi John,
I agree with Donald, the window is a killer for quality, especially if double glazed (you don't say whether building or auto glass).
Your 70-300mm on a crop body, is going to be equivalent to 490mm, so should be closer than the P90 at a (35mm equiv) of 353mm, assuming I interpretted what you told us correctly.
But you'll need a firm tripod and good technique to avoid shake at that focal length on that kind of subject.
Cheers,
This is building glass, when the P90 is extended you can feel the barrel move. The P90 has a focal length of 4.6-110mm and has 4X digital zoom. I need a better tripod for sure and I will have to wait until the next clear day to try the 70-300mm lens. Thanks for the feedback, Donald and Dave.