Hi Grady
These seem to be quite different sorts of scopes to me...?
One will be excellent for wider field shots that will fit heaps in and capture it very fast, the other much slower but higher image scale for smaller objects like galaxies and smaller nebulae etc?
Generally an RC is more forgiving in the area of flexure and I think there is more examples of successful results using the RC8 though..but I haven't really looked for GSO 8" F4 images that might be out there? I imagine some modifications will be necessary to upgrade the 8" F4 Newt to take top class images least of which is a good corrector.
There is no doubt that having the speed at your finger tips is a god send when skies are limited and time is of the essence.
If you have the ability to save a little further you may consider an
Orion Optics 8" F4? These are excellent high end instruments, very well made and will give great results compared to the cheaper GSO 8" F4 and need no further modifications even for very large sensors sould you upgrade cameras in the future.
I have the AG12 and the ability to gather serious photon quantities in a very short time really is useful for a portable and sky time starved imager like myself
The 8" F3.8 would have a wider field and obviously a smaller aperture would make a difference but just to illustrate, this is just 1hrs worth of Ha using just 5min sub exposures from a light polluted sky with the AG12:
http://www.pbase.com/strongmanmike20...17179/original
Peter Shah in the UK has some great examples of AG8 images at his web site too.
Just some thoughts
Mike