Fits and starts in developing a revolutionary new inhaled insulin have meant that Al Mann's MannKind (NASDAQ:56400P706) has had more than its fair share of pops and drops over the past few years. MannKind won FDA approval for Afrezza last summer and announced its commercial launch earlier this month. The news has investors wondering if now is a good time to buy, but our Motley Fool experts think owning these three biotech stocks may make more sense.

Source: Insys Therapeutics.

Todd Campbell: Thanks to Sanofi's marketing might, I think MannKind has a good shot at finally monetizing its controversial inhaled insulin Afrezza this year, but for my money, I think Insys Therapeutics (NASDAQ:INSY) could prove to be the better buy.

Insys Therapeutics already has a fast-growing commercial drug on the market. The company's quick-acting fentanyl spray Subsys for breakthrough cancer pain saw its sales surge 105% to $58 million in the third quarter. The drug is the leading immediate release fentanyl drug in a market that Insys estimates is worth $471 million a year.

If the company can win FDA approval for its oral formulation of the anti-nausea drug marinol for chemotherapy patients, it could have a second drug with nine-figure potential on its hands in the coming year.

But it's not just Subsys and oral marinol that are intriguing to me; Insys is also researching the use of the marijuana cannabinoid CBD in epilepsy patients, and the company just reported that the FDA had granted orphan drug designation for a version of Insys' paclitaxel for potential use in ovarian cancer. With a growing cash stockpile, no debt on the books, and an intriguing pipeline, I think Insys Therapeutics could be a top performer.

George Budwell: MannKind's inhaled insulin, Afrezza, may go on to post blockbuster numbers, but IGI Laboratories (NASDAQ:TLGT) is a more compelling stock to hold for the long term, in my opinion.

IGI's story centers primarily around its talented CEO Jason Grenfell-Gardner. In 2012, Jason took over the struggling generic drugmaker and quickly instituted wholesale changes that have paid off in a huge way.

Digging into the details, IGI now sports 22 Abbreviated New Drug Applications, or ANDAs, on file with the Food and Drug Administration, with plans for submitting 1 to 2 per month in 2015.

The company has also dramatically increased and diversified its product portfolio under Jason's watch. Aside from its monstrous ANDA portfolio for topical generics that has already led to multiple new drug approvals recently, IGI has gone out and acquired 18 injected ophthalmic products from AstraZeneca and an additional 2 from Valeant Pharmaceuticals.

As a result, IGI is expected to become cash flow positive before year's end, and earnings per share are projected to skyrocket by over 400% this year. MannKind, by contrast, is highly unlikely to become cash flow positive anytime soon, despite an estimated 31% jump in earnings this year.

Keith Speights: Acorda Therapeutics (NASDAQ:ACOR) has a lower market cap than MannKind but claims one key advantage: It's already profitable. That's thanks primarily to multiple sclerosis drug Ampyra, which generated sales of over $366 million in 2014.

Look for Ampyra revenue to keep growing robustly. Acorda projects 2015 net revenue between $405 and $420 million. However, another factor that differentiates this company from MannKind could be a more significant driver for the biotech's stock.

While MannKind's fortunes hinge solely upon Afrezza, Acorda claims three drugs in late-stage clinical trials. The biotech is working with the FDA to define some additional clinical work needed for approval of Plumiaz, a drug that helps control bouts of epipleptic seizure clusters. Acorda also began phase 3 studies of dalfampridine, which targets treatment of chronic post-stroke walking deficits, and Parkinson's disease drug CVT-301 late last year.

Analysts think Acorda's share price could hit $45 over the next year -- a 25% increase over the current price. That seems very possible, especially considering that the stock was already briefly at that level in January.