1) Which Fpga is better out of those to synthsize into: Xilins Spartan
or Altera Cyclone?
Do you need any special block inside the FPGA? (BlockRAM (How much?),
MAC units, many multipliers, a CPU core, many clock buffers)
If you have thought about what you need and how big everything will
become, then you can chose the right FPGA.
If you are familiar with one FPGA vendor it is often easier to stay with
this one. If you already have the tools, it is cheaper if you continue
to use them. If you have colleagues in other parts of your company that
already use FPGAs by one vendor it is nice to go to them and ask them if
you have a problem, if you are using the same tools.
The FPGA tools should offer you synthesis to any type of FPGA from the
appropriate vendor. So you can easily chose a FPGA that is big enough.
For my opinion choosing the FPGA is a step that comes very late during
the design process. Often I spend months building my component and then
twice the time to test it in my simulation environment. And finally I
move to the desired target (ASIC, FPGA).
Let me give you an example: At the moment I do a design which has seen
two FPGAs: Altera Flex10k (so old that you could call it a dinosaur) and
Xilinx Virtex 5. My component only needs a "see of gates" and some
small amount of block RAM. It has a lot of clock gating (and the Flex10k
has only one clock buffer). The decision for Xilinx was because enough
Xilinx Software licenses are available in my company.
2) Is it better to write in Verilog or not and why?
If your boss did not make a decision for you: Use the HDL you are
familiar with!
I prefer VHDL, because it is strongly typed. This means small typing
errors will be detected as errors and are unlikely valid expressions
with different meaning.
Have a look at the book "HDL Chip Design" by Douglas J. Smith. It
teaches both languages at the same time.
Ralf