I may not have come across the totes you're talking about and sure hope they don't just buy any tote as the same could happen with the totes as with the dog crates. However the dog crates say if they are the airline approved ones.Those totes I linked are not flimsy. I know people who have shipped 50-75 lb. Aldabras and sulcatas in them. One of them is more than adequate and perfectly safe for shipping two 10" Radiated Tortoises. Anytime I have shipped more than one tortoise in such a container, I have fabricated partitions to keep the animals separated and protected from any injuries or shell damage.
Also, when using dog crates, the dog crates must be "airline approved" to be acceptable to Delta as I mentioned in my earlier post, so one bought off Craig's list may or may not meet the airline requirements, and an unaware shipper could be turned away on the day of shipping if the wrong type crate is presented and Delta does not have one available for sale at the time.
I missed the part where you say you seperate the tortoises with a partion or it wasnt mention.
Everyone will have their preference and as long as they are sturdy enough and properly packed it should all work. I like the dog crates as the animal can be seen without any one opening anything. I feel if they see the animal, when possible, not only is it easier to see stress but they are in awe of the animal and maybe will take better care to not toss it around, hopefully.