Generally, I think luggage shape is most important because having a good shape makes packing a wide variety of items easier and so one can most easily work around the potential drawbacks of the exterior materials. So my main bit of advice would be to get your checked luggage in some sort of trunk shape.

The shorter sides are by nature stronger while also presenting a smaller profile, making it a mechanically superior design that is also harder for other luggage to hit. It's also a big win for packing flexibility as the extra depth can handle a normal load of clothing and oddly shaped items with equal ease. Lastly the trunk's 80/20 opening makes living out of it or even simply unpacking it, a breeze.

To me the exterior material doesn't really matter all that much since most good manufacturers use quality polycarbonate, ballistic nylon, or their own high performance materials. However, I do prize interior setups which maximize user access to the space and flexibility in making style. So I shun interiors with strict or permanent divisions or "pockets". my personal choice for checked luggage is a rimowa essentials large trunk because of its light weight and dual packing "platters", which offer maximum flexibility and containment for my things. Unfortunately, afaik more recent essential trunks have reverted to the zipped mesh insert for the lid while retaining the "platter" in the main compartment, so I don't rate them as highly.

My other go-to checked bag is a completely formless folding nylon duffel, which is great for bring laundry home while the souvenirs ride in my trunk.