Welcome. As for your question: try your hand at both, but keep in mind one thing; is the story you're writing one that has just too much that can't be explained in a 90-120 page script? Depends on your genre. If your science fiction or high fantasy, likelihood is that it would be better as a book first. Things based in our world, or having something like Urban Fantasy, is easier explained. Or at least that's the way I see it.
Myself, I try to write both, and see where it takes me. My current WIP, a horror novel from the POV of a serial killer, started out as a screenplay similar in nature to Wes Craven's Scream. Now, it's much more different.
If you can handle both arenas (Hollywood and Publishing), than kudos to you and I wish you well. Myself, I'm more likely on the novel side of things. It'd be cool for me to see my writing on screen, but the truth is the likelihood of it being on-screen and not just bought without being produced is high, especially in today's world. (Just so you know, I'm a bit of a cynic, so take whatever I say with a grain of salt unless it rings true).
Anyways, it is almost five a.m. where I am, and I've just begun re-writing my horror novel from scratch, so I've got to get a move on. Again, misstypewriter, welcome. This community is welcoming to all who endeavor to entertain.