Almostboatless, I don't have the trailer you are looking at but know several people that do own a Sundance and are very happy with it. If you want to come over to the http://www.heartlandowners.org/content.phpHeartland Owners Forum, you will find many others that can answer your questions.
I think you're wise to be considering the Big Country. You said you "may" go full time in the future. Buy the new, lighter weight trailer to try out the RV lifestyle, using a lighter truck to pull it and then make your decision. Come on over to the http://www.heartlandowners.org/content.phpHeartland Owners Forum, it's free to join. There you'll find other owners and users of trailers like your's and willing to share experiences and recommendations.