If it were OPTIONAL, would you choose to do it?
Yes I would.
What are the PROS? Cons, if any?
It encourages communication (which should already be there if you're getting married) and it may bring to "light" certain issue or discussions that the couple may not have even thought to discuss.
If you wanted it, but your mate didn't, then what? or vice verse, mate wants and you don't?
Hmm, as someone else said ,
RED FLAG!!
Spiritual or non spiritual form of counseling?
Why spiritual of course!

- Seriously though, I plan to honor/fulfill my marriage according to the Bible, so a Christian counselor would be aligned to those beliefs.