Depends on use. Filling a rudder
, go for the heavy closed cell. Refrig insulation
, non structural, go for closed cell, weight according to the R value you need.
Space in a refrig can expensive and limited so if you have limited space use a higher R value. Eventually water
will get into open cell refrig insulation.
When I insulated the attic of my house I used open cell under the roof and closed cell in the knee walls.
The open cell was cheaper and roof leaks
are visible from the underneath so they can be found and fixed. Imagine finding leaks
in the roof with closed cell.