Hi Anthony
Sorry to hear that the dob is not being used. The 2 scopes you have highlighted as with all svopes have pros and cons.
Firstly the refractor. About the only pros I can think of are 1. you will not need the collimator 2 it has go to 3 it may be slightly more portable than your dob. The big con is that it is a serious step down in aperture. It is only 4" so you are reducing your available light by nearly 4x. You mention light pollution, a small scope will only exerbate that problem.
Next the 6" newt. This is essentially the same scope as your dob (they are both newts) just 6" instead of 8" and on an EQ mount. The cons are 1, It is probably as heavy as your dob if you are using the EQ3 mount. 2. You will have to learn to polar align. 3. Newts on EQ mounts give you some "interesting" eyepiece positions. If you enjoy kneeling on the ground trying to look vertically up into an eyepiece, this is the scope for you!!
4. You will still have to collimate. Pros 1 you will learn abit about using an EQ mount if you decide to get into imaging 2. If can be retrofitted for go to.
Quality wise both scopes would be OK, its suitabilty that is the concern. I would urge you to perservere with the dob, there is a reason they are IMHO the perfect beginners scope!!
Hope this helps
Malcolm