I think it depends on the energy level of the traveler at the time of the trip. AZBuck is an accomplished roadtripper with a proven penchant for off-the-beaten-path exploring, but a state like Alaska can be daunting for even the most adventuresome of travelers. I have utilized both forms of travel in AK and I prefer my own wanderings -- when I can. Thanks for stopping in and sharing your expertise and ideas!
I have a couple of other planning tips:
Bring a good telephoto lens -- I have friends who have captured some amazing photos of grizzlies, caribou and other large animals right from the Alaskan Highway (without getting out their trucks...)
There are some game refuges that enable up and close and personal viewing of some of the magnificent animals that call Alaska "home".
Yukon Wildlife Preserve (near Whitehorse, YT)
The Large Animal Research Station in Fairbanks
The Musk Ox Farm near Palmer
The Alaskan Wildlife Conservation Center
Denali National Park....Hard to forget this place!
The weather is very changeable -- bring lots of combinations of clothes to enable layering.
#1 Best Advice: Alaska is not like a theme park -- it is very much an evolving place for visitors -- ferry schedules can and do change often, weather can be darn right amazing and can affect roads at any time. Alaska summers nearly always mean HUGE wildfires and so smoky conditions and some road closures are the norm. And there is always road construction underway....
Mark