I would take the Buell. Don't know much about either model, but have ridden Harley Touring bikes for years. I love them, they are excellent tourers. Not sure how they would handle the roads in Alaska though. I fear the RG might not fare as well as the Buell. I have spoken to an old fellar at the dealer that rides his Buell Ulysses everywhere and swears by it. He has taken it on several long trips up to Maine and has no complaints.
There is a Goldwing forum (gl1800riders.com) with good videos and pics of guys that have riden to Alaska. Check it out. Just do a search for "alaska", you will get plenty of hits. Probably shoot one of those guys an PM and they can give you advice as well.
Either way sounds like you have a great trip planned. Keep us posted.