It would be helpful if you could precisely describe exactly what it is that makes ST3 look better for you than emacs or vim.
Saying that "I can clearly see the difference" and calling it a "nice modern UI rendering/feel" is too vague to be useful for improving emacs or vim in any concrete direction.
I can see the difference too. For whatever reason, text in Sublime with the same theme looks sharper than Vim (Yosemite). Maybe it's because it's not surrounded by ugly text rulers and inverse mode split bars, or maybe the text itself is actually sharper. Who knows? The programs are free, try it yourself.
Also, both Vim and Emacs feel really chunky and numb when showing completions and switching buffers. They take many hundreds of milliseconds to respond to keypresses, while Sublime responds close enough to instantly for me to not notice. It makes a big difference for something that's done hundreds of times per day.
(That said, I'm still using MacVim as my primary editor. The botched ST2->ST3 transition demonstrated above all else the danger of proprietary lock-in...)
Saying that "I can clearly see the difference" and calling it a "nice modern UI rendering/feel" is too vague to be useful for improving emacs or vim in any concrete direction.