After watching this issue--a 10 or 12 incher, I agree with some conventional wisdom that I have picked up over the years. There are many advantages to a solid tube Dob--as long as it is 10 inch or smaller. Twelve inches and larger should be Truss telescopes. A 12 inch (or larger) solid tube Dob is difficult to fit into many vehicles, and it is quite clumsy to handle. I own a 12.5 inch F5 Portaball, which is a truss telescope, and it is easy to store, will fit into any vehicle, and is easy to set up and take down. I believe it is the 'hassle' factor that kills many people's enthusiasm for getting out and viewing. Everyone has a different tolerance factor for hassle. Too small a telescope will not reveal as much as a larger one. One exception with this comment is that a lot of people view with 2 to 4 inch refractors, and swear by them. Just check the refractor's CN forum. However, when you move up to six inch and larger refractors, then the hassle factor looms. The same for SCT or Macs. An 8 inch SCT of Mac will show a lot of stuff. They are easy to store and set up. They make great telescopes for camping and other outdoor venues. However, when you get up to 12 inch and larger, they can be a handful. You will meet people who view with 20 inch and larger Dobs, and have vehicles, and ramps, and ladders, and so on, and don't mind the hassle.
For me, the 12.5 inch Dob is perfect. Many refer to it as the 'Goldilocks' telescope because it is just right. A 12 incher has twice the light gathering capability of an 8 inch. That is significant. At the eyepiece, viewing objects through a 10 vs. a 12 incher, you will notice that there is not a huge difference whether viewing planets or deep sky objects. Of course, there is a difference in that the 12 incher is pulling in more light. However, going from an 8 to a 12, one will notice a considerable difference, especially when viewing deep sky objects; maybe not so much when doing planetary viewing.
Several years ago, I bought an 18 inch Ultra Compact. I had high hopes for this telescope. Its footprint was not so much different from my 12.5 inch Portaball. However, with the Portaball, I could easily set my telescope in the vehicle, with loads of room left over for tables, eyepieces and other accessories. Not so with the 18 UC. It required ramps which take up a lot of room. Its performance on planets was not as good as with my 12.5 incher. I did all the proper cool down, ran fans, and so on. I attribute that to the Portaball probably having better optics. Of course, deep sky objects were brighter and more pronounced with the 18 UC. One take away from all this is that I agree with whomever said on Cloudy Nights that the best accessory for viewing--is a tank of gas. Getting out to a dark sky site maximizes my 'Goldilocks' telescope. After about six months of A B comparisons between my Portaball and my Ultra Compact, I sold the Ultra Compact. My smaller Portaball gives its all, and I will never part with it.