Valeant Pharmaceuticals (BHC 0.35%) is trying to buy Allergan (NYSE: AGN) for $47.5 billion with the help of billionaire William Ackman, which, with his investment fund, bought almost 10% of Allergan to get a foot in the door.

Last week, he had a presentation with Valeant CEO Michael Pearson where Ackman presented an interesting slide with a laundry list of reasons not to invest in drugmakers.

In the video below, senior biotech specialist Brian Orelli and health-care analyst David Williamson go through the list, discounting many of Ackman's points. For instance he cites patent cliffs as a problem, but investors know that they're coming; everyone could value Pfizer (PFE -0.19%) properly knowing when generic copies of Lipitor would launch, impacting Pfizer's revenue.

Ackman also complains about pricing pressure, but Gilead Sciences (GILD 0.07%) has been able to launch its hepapatitis C drug, Sovaldi, at $1,000 per pill and despite a decrease in prescriptions Merck's (MRK 0.10%) diabetes drug franchise, Januvia, U.S. revenue increased year over year in the first quarter thanks to a price increase.

While Brian and Max might not agree with Ackman's general take on the sector, they're more content with his positive view of specialty pharma -- companies that sell smaller drugs that they often acquire rather than develop internally -- and offer up some specialty pharma companies that investors should keep an eye on.