DW is actually very slightly less EB (but earned at a more steady rate) than 2H. This is because 2H gets +40% attack speed which overcomes DWs apparent advantage (DW: 3 per 2.6 vs 2h: 3 per 3.6). After the +40% 2H is 3 charges per 2.57 sec.
Clarification: When I say "3 per 2.6" I don't mean it literally unless you have 100% crit, but both numbers scale the same with Crit so it's just a quick way to explain it.