This sounds like an absurd question, I know, but when I go to:
There isn't a download link! I'm sure it used to be there :-/
Here's what I see:
Scrolling further just has more features. No link!
Safari for Windows – Where to Download
safariwindows
Related Solutions
Anything involving the multi-touch track pad is going to be different, since that is an OS X feature. Including the double finger gesture to scroll back or forward.
In fact that feature works so seamlessly in Safari for Mac that that's one of the reasons I might switch to Safari from Chrome. It integrates beautifully with all the latest features of OS X.
The difference is likely to do with the architecture and interprocess communication choices of each browser.
Modern web browsers render pages in separate processes. Apple has a framework called IOSurface that provides a streamlined way for one process to pass an image to another process. This framework was introduced in Mac OS X 10.6, aka Snow Leopard, for the latest iteration of QuickTime.
QuickTime uses IOSurface to offload movie decoding to separate processes. With no decoding to do, the QuickTime Player application is left dealing solely with the user interface and showing images provided by the decoding processes.
I suspect Safari has learned from QuickTime and is using the same techniques. Web pages are offloaded to other processes, rendered, and passed back.
Could Chrome and Firefox do the same thing, absolutely. The challenge is ensuring the thread dealing with the user responds quickly and is not delayed waiting for the rendering to update.
Chrome does use separate processes and appears to use IOSurface on the Mac; this bug talks about improving Chrome's use of IOSurface.
IOSurface is a public framework available to any Mac OS X 10.6+ application. However there is little documentation and it is Mac specific.
This is all conjecture.
Best Answer
Safari on Windows is no longer supported by Apple.
Safari 5 (from 2010) is available via Apple's KB. The original page no longer exists, but the EXE is still hosted.
According to 9to5mac, it seems that have Apple decided to stop producing Safari for Windows, so Safari 5 is all that's likely to be available moving forward.
Update: As mentioned at Geek Dashboard, better use a cross-browser testing tool if you just want to test your project UI. With this, you will have the latest version of Safari running right in your favorite browser.