As the market continues to flirt with all-time highs, a considerable amount of churn is taking place beneath the surface. Investors are increasingly flocking to companies that are seemingly big and safe, while shedding exposure to smaller and riskier names.

It's a logical move, considering the current bull market is getting along in years. Indeed, I extolled the virtues of mega-cap stocks back in August, and you can still find some great bargains among America's largest companies.

Yet if the market is going in this direction, it also means that smaller stocks are falling to levels that hold real appeal. And in no sector is this divergence more apparent than in biotechs. The biggest biotech stocks appear fully priced -- while their smaller brethren are now far from their 52-week highs.