When I was experimenting with going wide, I used four different aggregators, Each had some unique outlets, but I did all four primarily to see how the processes worked. I used D2D, Smashwords, PublishDrive, and Streetlib.
All four worked reasonably well, but I preferred D2D's system. I also like the fact that D2D seems to be expanding into other author services, like its universal links.
Of course, the problem with any aggregator is that instore promotions, like Kobo's, are typically only available if you go direct. However, in recent days, I've seen evidence that some of the other aggregators are stepping up their game in this respect--but not D2D.
Here's what I've seen. First, Streetlib emails to say that any book distributed to Kobo through Streetlib will be eligible for the Walmart promotion. Second, PublishDrive emails to say that, from now on, all PublishDrive titles are eligible for any instore promotions.
Am I confused, are these two aggregators mistaken, or are they really able to interact with the retailers in ways D2D can't? (I've asked D2D about working toward making their titles eligible for instore promotions, and I've gotten a "We'll take that into consideration in the future" kind of response. If other aggregators are really doing it, and D2D somehow isn't, that would change my opinion about which one to use as my primary channel.