webcomponentsjs

This is the chart that matters: https://github.com/WebComponents/webcomponentsjs#browser-sup... Polymer, via the web components polyfills, supports IE10+, Safari 7+, Chrome, Firefox, and Android Browser. The chart you linked to is for _native_ web components support, which is better because it's faster and more spec compliant, but not necessary. The polyfills are quite good. (btw, you're linking to the 0.5 docs, the 1.0 doc is here: https://www.polymer-project.org/1.0/resources/compatibility.... )

For me the biggest difference is browser support. With React many libraries I have seen you can get pretty much running with IE9+ (often also IE8). In comparison Polymer: You need more or less the newest IE browser to get it working fully: https://github.com/WebComponents/webcomponentsjs#browser-sup... At the moment I also see that React has the bigger community/ecosystem but this may change in the near future?!

For me the biggest difference is browser support. With React many libraries I have seen you can get pretty much running with IE9+ (often also IE8). In comparison Polymer: You need more or less the newest IE browser to get it working fully: https://github.com/WebComponents/webcomponentsjs#browser-sup... At the moment I also see that React has the bigger community/ecosystem but this may change in the future?!

This is actually not true. If you're using polymer with the full webcomponents.js polyfill, there's a known bug which breaks contenteditable execCommand calls (which means a lot of rich text editors break when you include the polyfill) [1]. The big heavy polyfill is also pretty slow on some browsers. If you use the newer, lighter-weight shady-dom version of the polyfill, which is a lot more responsive on non-Chrome browsers and doesn't introduce the bug indicated in [1], you must do all DOM manipulation via polymer's local DOM api, in order to properly distribute dom elements.[2] That means, if you want to use polymer, you cannot use angular or ember (for example). Specifically, DOM manipulation via those libraries ends up just using regular calls against element.appendChild, but those appended elements, if they are polymer elements, end