My Cardio 2 had the short tubing and I really didn't like it (sometimes I had to actually switch sides of the bed mid-assessment, esp on obese vented/sedated patients. Did love the way the short tubing sat on my neck though.
Anyway, besides being short, the tubing was the old style (very heavy) and had become stiff. So I ordered replacement tubing recently and came across an article-
http://www.steeles.com/catalog/length.html
http://www.themedsupplyguide.com/stethoscopes/faq1.html
sounds like it's personal preferance and comfort.