I have a 7x50 and am happy with that combination on my 8" dob. My opinion on your question is that it depends a lot on what you are trying to view and your experience level. If you have quite a bit of experience, are comfortable finding your way around looking through a finder scope and are seeking some of the more obscure deep space objects you probably know you want a powerful finder scope. An experienced observer can cope with a narrow field of view. The 6x30 has a wide field of view which makes finding your way around much easier. You can see more stars to help you keep your bearings. Using a Rigel finder is easy because you can see all around it. Using a finder scope is like trying to find your way around in the woods at night looking trough a toilet paper tube. It takes a little getting used to at first. But my Telrad is actually sitting in a drawer right now, I like using the finder scope better. My old 6x30 binoculars will give me more visible stars than my sky atlas has recorded and would provide plenty of magnification for basic telescope use such as completing the Messier list. The 9x50 is much bigger and heavier than the 6x30 which is another consideration. Believe me, the 6x30 will be much easier to use if you are just learning to use a finder scope.