Hi there again, Hulagirl! yes, they are definitely two different and competing rides!! Some people would only ride one or the other!! There would definitely be a case for you to do BTC as you would have a good week off from your half ironman...and you would really need it. These are big climbing rides with some long days. Both the Colorado rides are great and they both fill, BTC, less quickly and without the lottery. Hope you get to go. It is really FUN!!! ...and the scenery is absolutely spectacular...the people are really nice (aren't all cyclists!!!?) GO FOR IT!!!