If you can physically manage it a 10" over an 8". Collects 56% more light (so brighter DSOs) and 25% more resolution (great for picking up finer detail on moon and planets, plus gives better resolution for DSOs as well).
I was faced with the same quandary recently, was a bit worried about the manageability of a 10". I'm not too old (just the wrong side of 40), but have a bit of a dodgy back. I decided to go for it and get a GSO 10", and haven't regretted it. I don't think I would want to hulk anything bigger around though.
Main concerns I would say would be weight, and whether it fits in your vehicle. Mine fits across the back seats of my car (Toyota Caldina). Is pretty cumbersome to get in and out of the car on my own, but perfectly doable. Unless you live in a dark site, you are going to need to get it out of town to use it to its full potential, which means being able to get it in your vehicle. So definitely check that out.
Go the 10" bloke. I've had mine 10 years and still get a kick out of it. On the prospect of clear and Cloudless night , my heart still flutters as I set up at my favourite deep sky site . One thing my scope excels at that the that the big boys don't is those awesome wide field views of nebula star clusters and galaxy clusters in one FOV
in one FOV
