If you opt to go for the caravan, do it because you want the caravan experience (traveling with same group, planned itinerary, someone else doing some of the prep work, etc.)
As many others have said, the trip is definitely doable on your own.
Inquire into what level of adventure versus luxury the caravan is striving for. There are plenty of unique opportunities boondocking and heading down some gravel roads which many caravans will not include, as their clientele is looking for the full hookup campground every night. Read through this forum and you'll see that most Alaska campgrounds are not as luxurious as those in the lower 48.
The above paragraph could also apply to traveling with another camper. Yesterday I was talking to someone from Outside traveling with 2 rigs--one wanted to venture off the paved roads more (see places like the Denali Highway, Kennecott mine, etc.), but was being held back by the other one who didn't.
There are many ways to see Alaska. Pick the one which suits your interests, sense of adventure, and budget.
