The Quad is a different board than the ET but I think the ET is also very good. ONe way the characterise the "magic" of the Quad is that it combines many very spectacular wave riding traits with very very good "performance" (planing, upwind etc) traits. The ET is a more normal type of compromise. It turns very well too and I would say it planes pretty early and goes upwind well too, but not with the same super ease as the Quads. But for an experienced wave sailor the relevant difference is more the type of turn once on the wave, where the ET is basically super loose and the Quad is more about drive (but in loose way).
If you're kind of light, I would also look for an ET70 which is a board with spectacular range that can replace both the E70 and E74 up to at least 5.3 sails.