Everything a Uno can do a Leonardo can do.
On the other hand, the serial port must be opened using DtrEnable, to talk to the Leonardo. If MATLAB does not use that flag, it can't communicate with the Leonardo.
Has someone tried of getting Leonardo to work with Matlab, and even succeeded in that?
In Python it seems as easy as putting:
comport.DtrEnable = true;
So now one should probably modify the Arduino class (arduino.m of the Arduino I/O package) in similar manner? Or simply set the DtrEnable flag to true for the Matlab programs you are about to develop?
I don't have yet Leonardo and was thinking of purchasing one also to be used with Matlab so if someone can confirm in advance that it has worked, it would be great