In any rig, TT or 5er, I like the kitchen over the axles. The axles are at the center of rotation of the trailer so that stuff does not get thrown about as much. The kitchen with its pantries, fridge and cooking and table utensils probaby has the most variable load in the trailer bar the tanks.
That said one would hope that the trailer mfr would compensate for a rear kitchen's weight and variablity since a tail heavy trailer is an unstable traiiler. However, I aslo have a lingering belief in the Easter bunny and the tooth fairy.