My prime choice would be Mathematica. Although Maple is said to be very "evolved", my opinion is that it is no where near Mathematica. Maple is very tedious and even its interface is very unfriendly to the eye. Although I have tried to use Maple, I could not stop to constantly think of the advantages that Mathematica had over every single task that I was carrying out in Maple.
Although both allow you to do pretty much the same things, Mathematica has many more in-built standard mathematical functions. Also the main advantage of Mathematica is that it is much more graphical than Maple; for example, when one wants to create a certain matrix in either of the programmes, the advantage of Mathematica would be that you would open a pallette which would allow you to, almost insert a matrix onto the screen and all you would have to do is enter the appropriate numbers; while in Maple one would have to enter a very long code. In this case, the efficiency of Mathematica would be very easy to notice when for example, creating a 10x10 matrix.
Another example would be when you are trying to integrate a function. In Mathematica you would just click on a symbol in the appropriate pallette and it would actually bring up the elongated sigma along with little boxes where the function and the limits would be entered. While in Maple, a similiar option is available, by clicking on the integral sign it brings up a code along the lines of "INT[%f(x)%,x].
This would eventually become very laborious especially when you are in a rush since the "%" signs need to be deleted along with the f(x), x1, x2 and ONLY THEN be changed to the appropriate values.
So overall Mathematica is much more efficient and it also allows you to do all the programming and even more than you would be allowed to do in Maple.
As well as the latter, Mathematica allows you to draw circuit diagrams, just by typing in the names of the components you want, and carries out a lot of Chemical calculations, like element mass and specifice heat.
As for MatLab it is a software used for a completely different matter.
Newton.