If you picked which stock to buy based solely on year-to-date performance, Incyte (NASDAQ:INCY) would get the nod over Vertex Pharmaceuticals (NASDAQ:VRTX). Both biotech stocks have been winners so far in 2019, but Incyte's shares are up a little over 3% more than Vertex.

But choosing a stock to buy only on historical performance isn't smart. You're much better off focusing on what lies ahead rather than what's in the past. Here's what you need to know about Vertex and Incyte to make a well-informed decision between these two biotech stocks.

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The outlook for Vertex

Last week was a huge one for Vertex's future thanks to two major developments. The company received U.S. Food and Drug Administration (FDA) approval on Oct. 21 for its triple-drug combination cystic fibrosis (CF) therapy Trikafta. Three days later, Vertex announced a reimbursement deal with NHS England for three CF drugs -- Kalydeco, Orkambi, and Symkevi, which is marketed in the U.S. and other countries outside of Europe as Symdeko.

The FDA approval for Trikafta came several months earlier than expected. This means that Vertex will hit the ground running quickly with a drug that can treat around 6,000 Americans who previously had no therapy that addressed the underlying genetic mutation causing them to have CF.

This FDA decision also bodes well for Vertex's approval prospects for its new drug in Europe and other regions. The biotech thinks that Trikafta eventually will be able to treat 90% of CF patients across the world. This new drug should expand Vertex's addressable patient population by more than 50% and could generate annual sales of $4.3 billion by 2024, more than all of Vertex's drugs make combined right now.

Speaking of those other drugs, Vertex's deal in England opens up the second-largest CF market in the world. The reimbursement agreement even ensures that England will cover any additional future approved indications for Kalydeco, Orkambi, and Symkevi.

While Vertex's global CF juggernaut marches on, the biotech hopes to expand into other indications in the not-too-distant future. Vertex should soon advance its pain program into late-stage studies. The company's early-stage pipeline includes several experimental drugs targeting rare diseases. Vertex's recent acquisition of Semma Therapeutics could even pave the way for the biotech to have a cure for type 1 diabetes in the future.

Vertex's sales and earnings continue to skyrocket, up 25% and 29%, respectively, in the company's latest reported quarter. Wall Street analysts project the company will deliver average annual earnings growth of more than 38% over the next five years.

The outlook for Incyte

Incyte's crown jewel is JAK inhibitor Jakafi (ruxolitinib). The biotech markets the drug in the U.S. on its own but licensed rights to Novartis outside the U.S. and receives royalties on those ex-U.S. sales.

Jakafi has won FDA approval in three indications so far, the most recent coming in May 2019 as a treatment for acute graft-versus-host disease (GVHD). Incyte thinks it can add to the list of approved indications with pivotal clinical trials under way for Jakafi targeting chronic GVHD and essential thrombocythemia, a rare disease where too many blood platelets are produced It's also conducting a phase 2 study of ruxolitinib cream in treating atopic dermatitis.

But Incyte's growth prospects aren't limited to Jakafi. The biotech claims two other already approved drugs for which sales are climbing. Iclusig, a leukemia drug that Incyte bought from Ariad Pharmaceuticals, continues to pick up sales momentum. New immunology drug Olumiant, which is licensed to Eli Lilly, is also rapidly gaining traction in the marketplace.

Incyte plans to file for FDA approval before the end of 2019 for pemigatinib in treating cholangiocarcinoma, a cancer of the bile ducts. It's also evaluating the drug in treating bladder cancer. In addition, the biotech is conducting multiple phase 2 clinical studies of parsaclisib in treating various types of lymphoma.

Revenue hasn't grown very much for Incyte recently, with sales increasing by only 1.6% year over year in the second quarter. However, the company's adjusted earnings jumped 19%. And with new indications for Jakafi potentially on the way and added contributions from other drugs, Incyte's future looks much brighter. Analysts think Incyte could generate average annual earnings growth of 44% over the next five years.