A few thoughts:
- I believe the Skywatcher 2 inch focuser is a rack and pinion. I also believe the XT-6 focuser is plastic, at least the body. In my mind, a 2 inch focuser versus a 1.25 inch: the 2 inch is m9ney in the bank, you don't have to use it but it's there if you want it.
- I think the 8 inch F/6 is worth considering. The OTAs are about the same length, the bases are about the same size and weight, only the 8 inch OTA is heavier but its about the weight of the base. I always move tube Dobs in two pieces, the OTA and the base so an 8 inch is not much more effort than the 6 inch.
- The 8 inch mirror adds significant light gathering and resolution but additionally, it will come with better components and accessories.
The Apertura AD 8 is about $470. It comes with a 50 mm RACI finder, a decent 30 mm 2 inch wide field and a quality 2 inch, 2 speed Crayford. New the finder is $60, the eyepiece $65 and the focuser $135. The finder is something one will want, some sort of 2 inch wide field is something one will want and the 2 inch Crayford, it is a very nice thing to have.
Yes, the 30mm GSO Superview is not the best 2 inch wide field eyepiece ever made.. But from my point of view.. I do have the arguably the four best 2 inch widefield eyepieces ever made, the 41mm and 35mm Panoptics, the 31mm Nagler and the 21mm Ethos. I also have the 30 mm GSO Superview. It's not as perfect as the others but it is effective, enjoyable and capable.
With the Apertura, you are getting these things in addition to the 8 inch mirror.
There is no doubt a 6 inch Dob is a very capable first scope and one often recommended. But my gut feeling is that for most an 8 inch is a better choice because it's just more capable. With the 6 inch, you will be buying things that come stock with the 8 inch.
It's getting dark, the skies are clear.