That's because Good or Bad is highly subjective. I happen to prefer long steering trail on tandems, but then again my wife and me are relatively compact people: 5'8" @ 160 & 5'2" @ 110. Going from our Santana with short trail to our first Erickson with long trail was a dramatic shift, but at the end of the day the Erickson tandems have always been preferrable.

Which DO YOU prefer? Here's how I have characterized them in the past.

Shorter fork trail on a tandem (e.g., Santana) favors low speed maneuverability by providing lighter steering effort and faster steering responsiveness to handlebar inputs. Many teams will describe this as being "more stable" because, at least at slow speeds, it "feels" that way. Tandems with shorter fork trail take less effort and attention to steer in a straight line at slower speed and are resistant to inadvertent movements by the stoker, aka (stoker induced steering). However, tandems with shorter trail also tend to understeer in aggressive or high speed cornering maneuvers which is not always desirable.

Longer fork trail on a tandem (e.g., Co-Motion with Wound-Up Fork) favors high speed cruising and aggressive cornering. This is because of their inherently greater straight line stability and smooth responsiveness to leaning inputs and countersteering. Many teams will describe tandems that handle well at speed as being "more stable" because, at least at higher speeds and for aggressive cornering, it "feels" that way. However, at slower speeds, steering tends to be heavier and less responsive which is often described as being twitchy. Moreover, for teams with stokers that are exceptionally tall, or who tend to move around along or "rock" when they ride, a tandem with long fork trail can make steering control a laborious task that can also be undesirable.