Neither are the "best". Perhaps look at it another way?? Longer is better perhaps with a double landing excellent if you have the time and money. Glaicers are in a constant state of change- Mendenhall is no better than any other icefield in Juneau - just more well known. If going on a costly tour prevents you from another due to funds- consider the single glacier landing- with Coastal starting at $180. In Alaska I'm a firm believer in VARIED experiences.