Hold your 'refresh' button down in SmartSearch bar, it'll give you the option for the desktop site. The 12.9" iPP IS faster than your '11 MBA. Go to desktop sites, then scroll, it'll haul ba&^lls! I've both the 12.9 and 9.7" iPPs and they're fast as hell on Safari. Crappy code can f a site up much faster than your hardware though (and in mobile, NO processors are beating the A9x's in Browsing/SnSpdr, et al).
You sir are a legend. Hopefully in time that option will be selected automatically.
For the above post. I also use ad blockers.