The Espanda rankings are actually ranking their reiatu; not just overall strength. That's why the big stupid guy went from Espanda #10-#0 because his reiatsu went up when he get's mad. The rankings were incomplete anyway; because as Ulquiorra said, Aizen didn't know about his 2nd release. So I'm sure he was atleast #3.
Barragan has a hax power; I'm still alittle surprised Aizen could get him under control.
Hallibel was so sexy before her release.
Because ulquiorra is actually the strongest espada. His resureccion segunda etapa was just rediculous. Ulquiorra shits on espada 0, 1, and 3, I'm not so sure about barragan now that I think about it tho
The espada are numbered by their reiatsu level, not their abilities. That's why Yammy is number 0 even though we know he's not the best out of all of them; he only has the basic abilities of an arrancars, nothing truly special of his own. (apart from transforming and growing bigger when he gets angry)
If Barragan faced Yammy, he'd wipe the floor with him.