Although biotech stocks as a whole handily outpaced the S&P 500 returns last year, there's no guarantee that investors will be similarly rewarded this year. To get insight into whether biotech stocks can continue climbing, we asked three top Motley Fool contributors to give us their opinion. Read on to learn what they think.

Cheryl Swanson: Bringing a new drug to market not only costs big bucks (a staggering $5 billion, according to Forbes), but only one in 1,000 drugs makes it to human testing, and less than 20% of those are ever approved for human use. This dynamic makes high drug pricing extremely important to biotech investors.

The recent deal between Express Scripts (NASDAQ:ESRX) and AbbVie (NYSE:ABBV) to exclude Gilead Science's (NASDAQ:GILD) pricey hep-C treatments set the stage for a potentially serious pricing war in biotech stocks. Gilead's shares slumped 14.3% on the news, and the company lost an astounding $24 billion in market capitalization.

Although Gilead recovered, playing hardball against high drug pricing is rapidly expanding. When asked what's next on his chopping block, Express Scripts CEO George Paz, speaking at the JP Morgan Healthcare Conference, said forthcoming bad-cholesterol meds (PCSK9 inhibitors) are "the short term, and cancer is a long term."

Biotechs are the stock market darlings for now. But if profit margins end up significantly lower than many anticipate this year, they could quickly fall out of favor. Bottom line: This sector is anything but crash-proof in 2015.

Todd Campbell: Cheryl's point regarding the risk of pricing pressure shouldn't be ignored, but I believe that those price risks will be more than offset by rising demand.

For example, Gilead Sciences and AbbVie will undoubtedly get paid less this year for their hepatitis C drugs than they would've gotten paid last year, but total script volume is likely to jump. In 2014, sky-high prices forced healthcare payers to ration access to Gilead Sciences' Sovaldi, but new exclusivity deals are likely to reduce the need for that kind of behavior. If so, thousands more patients with less advanced stages of the disease could be treated, and that could mean that overall revenue and profit at these companies heads higher, not lower. If I'm right, then investors may end up focusing more on that growth than on shrinking, but still healthy, margins.

I also think that biotech stocks could repeat their winning ways this year because of significant pipeline news flow. Biotech stocks tend to trade up or down more on tomorrow's potential than today's profit, and that may suggest that the significant influx of capital into the industry over the past three years -- and the corresponding surge in clinical-stage drugs in biotech pipelines -- could translate into a steady stream of trial data that keeps investors interested in owning stocks in the industry. 

George Budwell: Biotech stocks trade perhaps as much on optimism as anything else. And while the push-back from payers may dampen expectations this year, as Cheryl aptly notes, I think the commercial launch of several game-changing new classes of drugs, over the next year or so, should help to keep investors excited about the industry going forward.

On the cancer front, for instance, Bristol-Myers Squibb (NYSE:BMY) and Merck (NYSE:MRK) are both in the process of bringing a powerful new type of immunotherapy to the market, namely "PD-1 inhibitors." Although the initial regulatory filings for Bristol and Merck's respective drugs aren't exactly blockbuster material, they are expected to eventually generate revenues in the multibillion-dollar range, as their clinical testing for other types of cancers progresses.

And then there's the host of new PCSK9-inhibitors, coming down the pike from the likes of Amgen (NASDAQ:AMGN)Pfizer (NYSE:PFE), and Sanofi (NYSE:SNY). These next-gen cholesterol drugs are not only showing impressive results in terms of lowering bad cholesterol levels, but they're also exhibiting improvements in heart disease outcomes. If this trend holds to the final data readouts in the ongoing late-stage trials, these drugs could post monstrous sales numbers.

With the industry going through an unprecedented innovation boom, I think biotech will ultimately shrug off the pricing pressure issue and push higher in 2015.  

Cheryl Swanson and Todd Campbell own shares of Gilead Sciences. George Budwell owns shares of AbbVie and Gilead Sciences.  The Motley Fool recommends Express Scripts and Gilead Sciences. The Motley Fool owns shares of Express Scripts, Gilead Sciences, and JPMorgan Chase. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.