StoryOrigin is a bit more Wild West to me. This isn't necessarily a bad thing. In fact, I owe a great deal to them for some of their promos. But I think Bookfunnel is more well known. I also really like a lot of the extra functionality of Bookfunnel when gifting or creating ARC exchanges.
For newsletter and sales swaps, it really depends more on who's participating than which service I pick. I like to choose promos based on the marketing advertisement, the books, and the authors who I'm sharing with, not whether the source is Bookfunnel or StoryOrigin.
Ultimately, I'd love it if they both prosper. I like to provide my readers with different books and authors and, unfortunately, many of the same authors choose one service or the other.