They are all the same in memory. So, it really just comes down to which has the features you want, and which one loads quickest and most reliably.
B3D offers skinned animation, multitexturing, supports all Blitz effects: blends etc. The others (X, 3DS) definitely miss out on skinned and effects. Not sure about multitexturing. Also, I have noticed that sometimes X formats have worked on some machines and not others. This was usually solved by loading and re-saving in Unwrap3D or other.
B3D offers skinned animation, multitexturing, supports all Blitz effects: blends etc. The others (X, 3DS) definitely miss out on skinned and effects. Not sure about multitexturing. Also, I have noticed that sometimes X formats have worked on some machines and not others. This was usually solved by loading and re-saving in Unwrap3D or other.