Rather to compare E2E with Mac GpgTools, I'd try to compare it with https://www.mailvelope.com/ which is a much better comparison since both are addons for browsers.
Mailvelope works both on Firefox and Chrome (ironically, the Yahoo plugin seems to only have Chrome support at the moment) and is actually even nicer to use (read: seamless) than E2E IMO.
Mailvelope works both on Firefox and Chrome (ironically, the Yahoo plugin seems to only have Chrome support at the moment) and is actually even nicer to use (read: seamless) than E2E IMO.