If you are planning to do 100km a day, I really would endeavour to do that distance at least once, if possible with a fully kitted up and laden bike, but definitely with the saddle. In the UK, sure, but in New Mexico? Maybe not so much. If the comfort is the same, I'd suggest using the cheapest one. If you end up getting the Brooks shipped to you, a sub £20 saddle can disposed of without much thought (charity shop rather than rubbish bin trash can), but a circa £60 one has to be carried with you or packaged and shipped back. Either way, good luck with your adventure. One advantage I have notices with a Brooks saddle is that airflow through the holes and the leather itself means that things stay fresher on a hot day.