Recs.
Updated
SpecsUpdate
Pros
Pro Good source map support
To use source maps, go to right click -> show page source and you can use the document browser on the left to navigate scripts. If a script has a source map, an arrow will appear next to it. You can click it to expand the file to show the source map. If you need more help go here.
Pro Handoff and bookmark sync
Safari has a feature called handoff. This allows you to have a tab open on your computer, turn on your phone and swipe up on the Safari logo in the bottom left corner. Unlock your phone and the [tab should be open](https://support.apple.com/en-us/HT204681 for more details).
Pro Safari TP supports all ES2015/16/17 features
Safari is the first browser that supports all ES2015/16/17 features. (Currently the Tech Preview only.)
Cons
Con Proprietary
While Safari is currently available gratis (without monetary charge) on Mac OS X, it is currently not libre (meaning that it does not allow users to view the source code used to create, to modify that code, or to redistribute modifications) and is therefore neither free nor open-source software.