ED2 is useful if you are a legacy and didn’t apply ED1, either because you were improving grades or test scores or because you were rejected ED1 somewhere else.
And while few people here on CC would fall into this camp, there are seniors out there right now who are -gasp!- still working on a list of where to apply and doing visits. Oddly. I have encountered 2 in the last 2 days! Should they find one that rises above the rest, ED2 could be great for them.
As noted above, the pools tend to be different for each of the 3 rounds. I would be wary of making a decision about whether to apply ED1 or 2 based on the acceptance rates. However, if a school is your first choice, ED is a good option.
Remember too that if you aren’t a compelling candidate in either ED round but are qualified , many schools will roll you into the RD round. At that point, it could go either way, but the point is that you won’t be disadvantaged by being in the early round.