they are both the same length. about 1.1m the 10" is only fatter.
there is some decent information in here.
Pitfall. the 10" is heavier than the 8" and to properly mount it you will need a minimum of a EQ6 (though not really sufficient) at the lower end though a G11 is better or even a Titan for not the best mount but a sufficient mount for the shear size of a Newtonian. Photography is a gradual thing unless your happy to slip 4-5k for a budget beginner system and 5-7k for a intermediate system up front. much less than what i have just specified you'll be missing parts.
Coma in a 10" is nasty and unless you are using high end collimation equipment it starts on my images at about 50% image scale where as the 8" its 75% possibly a little further. I guess in the end its upto what YOU want out of it. the more you want the more you pay...
Though if i was you ide just go buy something I have seen that you have been filling your head with more and more information for a fair while now instead of actually getting out there and seeing it with your own eyes. It isn't till you get out and start using this equipment that you will learn what is needed for what it is that interests you. There will never be a "catch all" scope that will do everything that can be observed/photographed perfectly. You are on the right track with a dob.
save your sanity
Brendan