I agree with both Starcanoe AND Jon Isaacs. If one has the patience, time, and mechanical ability to set up a 12" F/5 scope, it's definitely going to be the better instrument in terms of performance at the eyepiece. However, it will never have the grab 'n go feel of a 6" F/10 instrument -- which is more likely to be 6" F/8 these days, but that would shift Jon's position down to a 10" F/5, and essentially the same argument.
A 6" F/8 or higher is a wonderful instrument. In a dobsonian mount, they are truely grab 'n go as anyone's 110mm refractor, and much more wind resistant than just about any refractor, period. The coma, tho there, is very, very small, and, I find, genuinely tolerable, unlike F/6, and especially at F/5, where, if you're using a Newtonian and care about a flat field, you've got to introduce a coma corrector, with its inherent weight on the focuser, and unique configuration issue-per-eyepiece, to say nothing of the extra stress on exacting collimation one concurrently moves up to.
For a more refractor-like viewing experience with less fuss, faster cooling, often better performance, the 6" F/8 newt is an unsung hero in the telescope world. Not the stunning galaxy viewer a 10" F/5 is, for sure, but more likely to easily split tight doubles than most 10" F/5 owners can muster. The 10" F/5 could produce every bit of star splitting capacity a 6" F/8 could, theoretically, only saying that the average 10" F/5 owner does not possess the patience, time, or mechanical prowess to make it happen, to say nothing of the extra thermal issues involved with a 10" mirror compared to a 6". And the weight of a 6" F/8 dobsonian is about the easiest "large-sized" telescope to set up a person can find, being amazingly wind resistant, but throwing up consistently good images.
Edited by CollinofAlabama, 17 September 2018 - 07:53 PM.