Assuming that you're meaning "professional" publishing of some sort, the answer on ease of use is easiest. Anything you know, thouroughly, how to do well, is "easy." All of the major "publishing" programs require significant amounts of study to be used at all with any real competence, but once you've learned how, the reasons that they're different from simpler software is because they make it "easy" to do common kinds of publishing work.
Anyone who has used a particular publishing program enough to know how to use it with some fluency likely will tell you that "their program" is the only one that's any good. You will find few people proficient enough with more than one of these programs to make really useful, and fairly unbiased, comparisons between them.
The choice of which program to use depends strongly on "who's your publisher." If you're intending to produce bound books, and will work with conventional production shops, many of the "book houses" have demanded that the ready-to-print job be produced on a specific program. Recently, in the past several years, some but not all of the volume printers have become significantly more flexible about accepting jobs in a variety of program formats.
In many places there has been quite a lot of "tradition" associated with which program should be used, depending on what kind of publications you worked on. "Academic Press" houses tended to use one group of programs, while "Literary Press" houses tended to prefer somewhat other ones. "Journal Press" - the ones who do techical and professional books and magazines often specify different programs, and some professional societies can be quite rigid about demanding a specific one. Magazine publishers choose differently than those who produce books. If you're in an "education environment" such as a university, the preferences are significantly different than elsewhere simply because of the much more universal use of "mainframe computer systems," which produces a preference for different programs than where most of the work is done on "unconnected" PCs and Macs.
If you are "thinking about writing a book," and expect to be working with a conventional large publisher, the emphatic answer to which publishing program you should use is NONE. The layout, formatting, and compositing of professionally produced books should be done by the professionals. Authors should submit unformatted plain text manuscripts and not muck them up by trying to make them look "pretty." Someone will have to figure out and undo all your "pretty stuff" so you should stick to a plain word processor and avoid getting fancy.
If you're intending to work with a smaller "indie" publisher, or intend to self-publish, you may want, or need, to put your work in a formatted form, and may need, or at least may benefit from a publishing program; but even there you'll probably find it easiest to use a word processor for composing your work and import it into a publishing program only for final formatting and layout.
If you may be thinking about those "office publishing" programs, then it doesn't make much difference, since those are for making viewfoils that managers can use to obscure the lack of content in a bunch of canned "prettiness" for dog-and-pony shows. 'taint "publishing."
Although you're likely to get lots of recommendations, you won't get useful ones until you provide a bit more information on why, and for what purposes, and in what publishing context you think you will use a publishing program.