check it out, there is way too many for a non-expert like me).
In the end, I think I made the correct choice by examining both the harder and the softer version, and let the arguments use the type most convenient, but it would still be nice to hear these things in advance.
Now, I still feel we are projecting too many modern values on this slightly different circumstances. Modern crates are placed in standard shipping containers, as are pallets, and the rest of the time they'd likely be in warehouses, so weather is not as much concern these days as it is minimising weight. Back in the day, cheap wood would be used for inside furniture, but anything that was meant to last in the elements would probably need a hardier wood. On the other hand, those tend to be slower growing trees, so they'd be expensive enough I can see a circus cutting costs by using substandard cages and have the animals living in leaky cages.