Hi Grant.
Theres a saying these here parts.
"Aperture is King" - particularly for observing. Unless your getting a 6inch triplet refractor, I'd choose a 8 inch newt/dob every time for observing. A little contrast maybe lost when comparing a 8 inch newt to a refractor but the extra light gathering power makes all the difference. About 77% more light I believe. That will make all the difference when looking at deep sky objects. If you just wanted to look at planets a 4 inch will do you nicely. Also if you get an 8 inch newt on a dobsonian mount it will be a hell of a lot cheaper then getting a 6 inch refractor plus an equatorial mount to put it on. Even if you only plan to get an Alt/Azi for the refractor it will still cost more. Resolution and light gathering power is also important for planetary viewing. By getting the newt the money you save can afford you some nice eyepieces.
However, in my opinion. Get a 10 inch Dob instead
