Altera has a clever way to create D-type Latch with NANDs so
it is best arranged , Also POF file format is protected and cannot
be reverse engineered.
That has always been at the absolute *bottom* of my priorities.
I try to make what I've done obvious. If you really need to hide
things Xilinx allow an encrypted data stream.
Xilinx has a ton of optimizations that may not be supported by
the common tools, but are there for the engineer (the carry
chains are quite useful, though not obvious for "random" logic).
but Altera software Max Plus is not free.
Ok. You want quality software, it's not going to be free.
in fact any PLD/FPGA depends on the design!
Not really. Many designs could easily be done in either. In
that case it's all about how you play the vendors against each
other. For some designs one might be better than the other. In
these cases, I'd guess Xilinx would take 80%. Their I/O is
simply superb (they bought an FPGA company out from under a
design of mine just for its I/O - very ugly; a complete redesign
at the last minute).