Short answer. Go the 8". Especially under your dark skies.
You'll really notice the extra aperture when you go hunting for Deep Sky Objects (DSOs) like nebulae, galaxies and star clusters. More aperture = brighter and better resolved faint fuzzies.
More aperture will also reveal brighter more detailed planetary images.
The more light you collect, the more you can resolve and magnify.
An 8" f5 is very transportable and as you've said comes with a 2" focuser with 1.25" adaptor so you can use both size eyepieces.
But listen to what others say coz you'll get plenty of good advice here. Ask lots of questions. Oh... and
