I have mwtal, hard injected plastic and 3D printed Roman artillery - scorpions, ballista, onagers, catapults etc. All are particularly usable on the wargames table. Since most of my games involve the grandchildren surviving the "drop test" is important. In which case the 3D printed ones are best then the hard plastic ones and last come the metal ones. The main reason, as far as my experience goes, is that the 3D printed ones have fewer parts to break or are one piece prints. Once painted and crewed there is virtually no visible difference. Assuming that a good 3D printer and stl file are used.
Incidentally I find resin almost useless for figures when playing out games when grandchildren participate - hard plastic or metal only.