Mailvelope is a much better choice if your goal is to interact with the existing OpenPGP ecosystem; E2E was using ECC keys only if I recall, which makes their crypto incompatible with many other OpenPGP setups.
The E2E promise was that with Google's backing, suddenly millions of people would/could encrypt and PGP would take a big step forward, making some forced upgrades in the rest of the community worthwhile. That is seeming less likely to happen now.
The E2E promise was that with Google's backing, suddenly millions of people would/could encrypt and PGP would take a big step forward, making some forced upgrades in the rest of the community worthwhile. That is seeming less likely to happen now.