I'm honestly not exactly sure about the background on Musa "Mekong Giant". It might be the same banana as Musa Itinerans var. itinerans but a more vigorous (and more cold hardy?) form of it. I've seen it marked as Musa itinerans var. xishyangbannaensis or just Musa xishyangbannaensis. Yeah so regardless not a very easy botanical name to pronounce. You'll see me call it Mekong Giant for know on though!
So what makes Mekong Giant different from a Basjoo? They are running bananas (don't worry not vigorous like bamboo - I hope!) so their pups are often much farther from the mother plant then you'd expect from a basjoo. The trunk also is darker colored and the plant itself is supposed to be more tolerant of shade and much faster growing. Cold tolerance should be similar for both. This is all other peoples opinions, hopefully I will be able to give you my own over the next few months, and if I am lucky, years.
So here's a pic of it newly planted next to an also newly planted fig tree. Ignore the state of this area right now. This entire part of the yard is getting replanted after my vegetables in this spot were destroyed by fungus.