Those resins are absolutely fantastic but do read the MSDS and be very careful, it doesn't take much to get yourself in the emergency ward with that stuff. Another risk to be acutely aware of is that these reactions usually are exothermic and can go runaway faster than you can blink of the conditions are right.
Of course, one should always read the MSDS. I use a 3M respirator with VOC inserts while working on these things. However, one should mention that a) polyurethane resins and platinum-cure silicones are much safer than many other compounds, and b) polyurethane resins are different from the more common epoxy resins and reactions are only very slightly exothermic. It's not a problem like when you're building a river table.
As a rough estimate, using a resin 3d printer is more problematic than these compounds.