Back in the early days of Ebooks (2001 - 2002), Rosetta Books (publisher of this edition) got into a much publicized legal battle with Random House.
The short version, RH claimed they controlled eBook rights as part of existing contracts with certain authors. Those authors, however, begged to differ and had made separate contracts to publish eBooks of their works with Rosetta.
RH took some hits in court and eventually the parties settled the case, with the two striking up a licensing agreement. Both sides declared victory, but Rosetta was still allowed to publish the disputed authors eBooks, so you decide whose spin was closer to reality.
Vonnegut is the only one, so far, that I can find that has eBook editions from both publishers, but I didn't really have time to perform a bunch of comparative searches.
As far as which one to buy, I don't think it really matters.
The one title I have from Rosetta (purchased many years ago from ereader.com back when I read on my Palm Pilot, now living nicely as sideloaded content on my NOOK classic) was of acceptable quality as far as proofing and other content issues. Rosetta does use its own covers, not the ones from the RH editions, if that makes a difference to you.
It remains to be seen if Rosetta's titles that are licensed from RH are governed by the agency model that RH has announced for titles under its own imprints.