I think the biggest advantage of going to Denali would be the wildlife viewing opporunities. But the problem is the amount of time that it takes to get there. Alaska's just too big - it takes a lot of time to get into the interior. It appears to be about 8 hours by the Alaska Railroad. Karen - it might not be so bad if we were on this level of service:
http://www.alaskarailroad.com/passenger/goldstar.htm Other options would include the Alyeska Resort
http://www.alyeskaresort.com/ which is 40 miles south of Anchorage. Looks like a really nice place but it's not Denali. :)
Kathy - which 4 night tour were you looking at? I didn't see it on the website.
Masaki