gitzo redesigned the 1541t and the 1542t replaced it. but the 1542t has a center column that folds down to the same length as the legs so it isn't as compact if you have a head attached. thus they introduced the 1544t, which is essentially a 1542t with a shorter center column...
the strange thing is that despite this fact, the final closed length of the 1542T and the 1544T are exactly the same (both are 16.73 inches). that's why i commented that i thought the 1544T had a double disadvantage, because you are losing the extra max height due to the shorter center column yet the closed length isn't even shorter. (for comparison, the 1541T has a closed length of 16.14")