Leornardo is atleast a step higher compared with XST.
ISE is a unique IDE for acheiving the whole data flow in an FPGA design, and so u cannot expect a very high performance from the same.
In my opinion, I would say Leonardo Spectrum is much much better than XST (xilinx) synthesis engine.
The reason is
-Leonardo was developed to synthesis and it's cost you a lot. Means, the synthesis engine is definitely very good compare to XST.
-XST is come with Xilinx ISE and even you can donwload ISE for free (web edition). The thing is synthesis engine or tool (Xilinx XST) is not their main product. They selling FPGA not a synthesis tool :wink: . While Leonardo is a synthesis engine.
XST is under permanent developing.
And each new version is much more speculative one.
Espscially XST recognizes many idioms which are mapped into hardware very well.
Because XST is adapted to Virtex architecture.
Leonardo has origined as the tool for the situation in general.
It optimizes logic very well. It is adapted to FPGA.
But it is not adapted specially to Virtex.
Therefore usually the designer feels what idioms are mapped very well into
hardware, and drives the project to the optimum structure.
The examples of these idioms are represented in the user manual.
And XST serves better because it recognizes these idioms very well.
It is very important in DSP applications where the logic minimization does not matter.