Saxon, Skywatcher, Celestron, Tasco, Jason, Konus - these and many others are owned by the one Chinese parent company, Synta. All their scopes are the same per model.
Bintel branded scopes are GSO in origin, a Taiwanese firm.
Andrews Communications also sells GSO scopes. Their 8" dob is $449, & is the same scope sold by Bintel.
Quality difference between these two? Bugger all really. These are mass produced instruments, so each will have excellent examples & poor ones. On the whole, it just comes down to your own preference.
I have to differ with you here for once Allan,
. Pyrex vs BK7 is more significant in apertures larger than 12", & more so for imaging than visual for the time that the cooling process happens over, & then no more problem (if the differences are really that significant). Any issues with expansion is quickly dealt with by a little fan if it really concerns you if you have a solid tube scope. My 17.5" has the primary completely exposed, & any cooling issues here in Oz, really is not significant enough to warrant complicating things with a fan, & the cooling that happens while I set up is as far as I consider 'cooling' to happen, & while I'm waiting for the sky to darken. I think we tend to fixate too much on cooling our scopes if visual is all we use our scopes for. Even a solid tube is a metal tube that dissipates heat very quickly, & the rear of the tube is not a sealed unit, making cooling really even less of the problem we make it out to be. Dew is more problematic than cooling as far as I'm concerned. We fan our mirrors to cool them & then heat them to keep dew off - nuts!