Traveling with a Super Tele is totally different than traveling with the zooms mentioned.
So no fair comparison there to draw.

When I travel with the 500mm I have a Pelican bag it fits nicely in to. It is carry on and I have never had an issue.
But any of the big whites is a chore to travel with.

When it comes to Supertele's of course the smallest is the easiest to carry.
Maybe the 400mm DXO II would be the option?


But IMO you are asking the wrong question. The question should be what is the ultimate lens for birding, whether or not it is difficult to travel with is beside the point. If it does matter are you building your trip around ease of travel, or having the ultimate experience while you are there? (considering it that way maybe from my perspective it would be the 500mm or 800mm will always be the ultimate big white for travel). All the lenses can travel, so how much work are you willing to put in to getting the ultimate lens there?