While ebook sales are increasing, and there are interesting marketing strategies you can pursue with ebook, I would publish in both formats.
Some people will still prefer a paperback format to an ebook. However, if it’s a question of publishing one or the other, then stick to ebook. If you publish your ebook on Amazon for example you can enroll your ebook in Kindle Unlimited, which can be a marketing tool to get more readers. If you simply publish on paperback format, I found the marketing options more limited (I’m speaking as a self-publisher). The price of a paperback is also higher than an ebook so it’s generally easier to convert new buyers to a lower price than a higher one. You can run offers of free promotions for your ebook, but if you do that for a print book you will have to carry more costs (not only marketing costs, but also printing and shipping costs!).
However, there is something very satisfying about holding your printed book in your hands. And when launching your book, most of the people you know will want to buy a paperback version so you can sign it, at least that was my experience. It also gives potential readers the choice of format. They may buy the ebook first, but they may like it so much that they will buy a paperback version just to have at home and display.
It may cost you a bit more in upfront costs to get a paperback done (you may need higher resolution on your book cover and you need to have a back cover as well as an ISBN number), but it’s worth it in my opinion.
You could also split the launches and do an ebook only launch first, and then a paperback one, which can help you get a bit of momentum going.
When deciding all of this however, you need to think of your target audience. Who is the book directed to? Young Adult? 18+? What is your book about? Is it a horror story or a self-help book? Do some research on your target audience, and check out the competition. You don’t have to do like the competition, but I advise you to at least be aware of the market you’re entering and have a vague idea of what your competition is doing.