Do you need to spin the cutter both clockwise and counter clockwise?
This depends on the cutter style. I have cut with discs, flutes and grinding style cutters never really needing to spin my cutter opposite. The cuts came out perfect spinning clock wise.
Do you need water to cool your motor?
I learned long ago the more you add to a system the more points of potential failure. The water filled tubes look cool but this adds more weight, another system to maintain and it buys you nothing when cutting pu/eps foams.
Spindles are less noisy for sure, however are much more expensive then routers, harder to find and are more drama to replace. Most watercooled spindles you will see offered are made in China which can be ok but there have been lots of issues with them. It depends on the manufacturer and importer to the quality and warranty. The warranty and ir replacement being the issue.
We select our routers based on other industry testing, feedback and results. Industry that is much harsher on components.
On surf style machines we recommend routers. They are easy to find, inexpensive, have great real warranty's due to the fact you can buy them from retailers and they actually last longer then some of the chinese watercooled spindles selling for $800-$1100. We have customers that have had their router spinning through medium production for 4 years! They replaced brushes year 2 for $19.
So in closing don't get fooled by someone pitching a product when they don't do research. They simply scramble to find something to be different that they have not tested. Precision Shaper Systems selects conponents based on facts not false information, sales pitch and uneducated feelings.