What: On Monday, ace stock analyst Longbow Research took a hammer to Shake Shack (NYSE:SHAK), initiating coverage of the stock with an underperform rating -- and helping send the burger maker's stock down. By 2:15 p.m. the stock was down about 4.5% from Friday's close.

So what: As reported by ratings aggregator StreetInsider.com, Longbow tore into Shake Shack just days after its earthshaking IPO. Blasting the company for showing "decelerating" same-store sales and a high stock price tag (now near $40), Longbow predicted Shake Shack shares could lose as much as 50% of their value through the coming year, falling to $21.

Longbow contrasted Shake Shack's excessive valuation of 4.5 times sales and 100 times earnings with the more modest valuation of a stock it likes better: Habit Restaurants (NASDAQ:HABT), which costs only 1.6 times sales and 31 times earnings, according to data from S&P Capital IQ. (Not coincidentally, Longbow then proceeded to recommend buying Habit.)

Now what: Longbow Research also told investors it sees better "new store upside" at Habit Restaurants than at Shake Shack, and pointed out that Habit's same-store sales are already growing. Altogether, this has most analysts predicting 25% annual earnings growth at Habit -- versus SEC-mandated post-IPO silence from the analysts involved in bringing Shake Shack public.

But are all these analysts right? Is Longbow?

According to our Motley Fool CAPS supercomputer, Longbow quite possibly is right about these two companies. We've been tracking this analyst's performance since November 2006. And we've found in that time that Longbow is one fine stock picker, outperforming 95% of the investors we track.

Indeed, within the Hotels, Restaurants, and Leisure sector, wherein both Shake Shack and Habit Restaurants reside, Longbow Research boasts a record of 80% accuracy on its picks -- and 427 percentage points' worth of market outperformance. Across five very precise picks made over nearly 10 years, Longbow has beaten the market by more than 85 percentage points per pick.

Simply put: If ever there were an analyst you'd want to tell you how to view the Shake Shack IPO, Longbow is it. And Longbow hates Shake Shack.

Source: Motley Fool CAPS.