Now now... let's be fair here. There are TWO zipline tours in Juneau.
is the alpine tour up by Eaglecrest Ski Area, and www.alaskacanopy.com
is the tour over by the Treadwell Gold Mine ruins.
I don't have a "favorite" of the two, but Alaska Canopy Adventures uses a jet boat to get you from downtown to their trailhead. I always choose boating over busing if given a choice!
There's also N. America's longest and fastest zip ride over at Icy Strait Point (Hoonah)... www.icystraitpoint.com/excursions_zip.html
My point is that there are MANY options for zipping in SE Alaska. Fit it in where your schedule allows.
It's also very common advice to suggest splitting up for the tour that you each want to do. The "experience" that you'll share is the wonderful dinner conversation while you relate your adventures to each other... to each their own.
Happy Alaska Travels!