Actually, Charly, I calculate my values for biotechs two separate times. First, I look at the pipeline and do the same sort of discounting calculations that you do, but then I pair those figures with book value. By looking at the price-to-book ratio, you can get a sense of just how much optimism is baked into a biotech stock. Argue with it if you'd like, but it's worked well for me and led me into several multi-baggers.

Moving on, we have the Nuvion issue. Simply put, folks, Charly and I are in vast disagreement about the sales potential of Nuvion. He thinks it'll be a phenomenal blockbuster. I don't. I agree that it will be a successful drug, yes, but I think $1.3 billion in sales is way out on the tail end of the probability curve, unless we happen to see a bout of Brazilian-style hyperinflation over the next five or so years.

But see, that's the wonderful thing about biotech modeling. Want to make a stock look cheap? Just pump the future sales potential of a drug by a few hundred million and watch that target price soar.

Simply put, if somebody came up to me today and offered to sell me all the rights to Nuvion for $10 a share, I'd laugh that person out of my office. What's more, by placing such a high value on Nuvion, Charly gives me another weapon in this duel. What happens if Nuvion craps out and turns into a big fat zero? I'll tell you what happens --Protein Design Labs (NASDAQ:PDLI) spends a day on the Nasdaq Biggest Losers list, and a good-sized chunk of its market valuation goes "poof."

I don't dispute at all the notion that PDL is a quality biotech investment idea. Frankly, I love the mixture of stable (and cash-rich) low-risk royalties coupled with high-potential pipeline candidates. But as in all things, price matters. The stock has already had a nice 50% jump up from its lows, and I just don't think we're in "good buy" territory any more.

Offer me the stock at $18 or below, and we'll talk. Until then, the risk-benefit analysis swings more to "risk" in this Fool's view.

Protein Design Labs has beaten the market a few times over since being recommended in the Motley Fool Rule Breakers newsletter service. The average pick has nearly tripled the S&P 500's return. You can take us up on a free 30-day trial to see what all the fuss is about.

Keep up with every step of the duel. Flash back to Charly Travers' original assertions, Stephen's return salvo, and Charly's bullish rebuttal. Once you're done, don't forget to cast your vote for this week's winner.

Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).