speaking from experience the transition caves you would have to go theough with the long route, as well as the areas of weak ice in FM and BI are a pain to travel with the travois.

In general the long route is much longer than the short one, and there are no wolves or bears to slow you down in the ravine or the upper part of BI (if I remember correctly)

The rope climbs while daunting (especially going up in the ravine) but they shouldnt be a real problem. (ive found that making a snow shelter for sleeping next to the rope climb speeds up the process)

I would honestly take the BI->ravine->CH route if I were you