So far I'm personally seeing way more engagement here on @ello and I've only been on it 5 days so far. Using the two fancy Denny's photos (1 & 2) that I posted today as an example, I've seen way more comments on @ello than anywhere else. And that's with far few followers here than all the other places, many of whom are not fully ramped up yet on @ello.
Here is a tally of comments on both photos by social network (likes/favorites not counted):
Ello = 14 (3 are mine in response to other comments)
Facebook = 6
Twitter = 0
Instagram = 0
Flickr = 0
All were posted to each network at the same time with the same caption, measured over a two hour period. Of course results will vary from person to person.
Of course I'm sure some of this could be explained by the fact that @ello is new, but I do think that this (at least for me) is an indication that they are off to a right start.