For the past few years I've bought both ebooks and pbooks during the same week. I can't tell you how I decided on the format in each case. Immediate availability and lower cost are certainly factors that favor e. Also, with about 4,000 pbooks in my home, I am running out of shelf space. E-space is limitless.
I really enjoy the convenience of ebooks. I am currently having a great time reading The Brothers Emanuel on three PCs, my Kindle Fire, my iPad and my phone. I hate the silly hyphenation and gaps between words, but love that Jeff Bezos keeps track of my reading progress and "opens" the ebook to the right page no matter which device I use to read it with.
As a publisher I was late to embrace e, but I came to love the use of hyperlinks, color without cost, low selling price with high profit, and ease of updating.
In the past, most publishers produced ebooks after the pbook editions, similar to what had been done with paperbacks following hardcovers. As ebooks became more acceptable -- and more expected -- the trend has been to simultaneously publish p and e.
I just published the ebook edition of Anthology of Third-Wirld Email Scams: Learn from the best and worst! (If you're interested and want a 'more perfect' book, wait until tomorrow when I've made a few corrections.)