I have built and gamed with resin, metal and plastic 20mm / 1/72/76th models for 30+ years, resin is the easiest to build and assemble but barrels and poky out bits can be fragile. Metal as mentioned can be fiddly to build but are more robust, plastic depending on the firm you are using can take a little longer to build but if based can be stronger than metal. If I was starting over again I would use Plastic Soldier Company tanks and vehicles they are easy to assemble and have robust running gear and wheels, which will stand up to wargaming handling with or without bases.
Three-quarters of my WW2 stuff is based but that started out as a necessity due to the weakness of Airfix / Esci / Revell running gear and wheels as mentioned the more modern plastic manufacturers running gear or wheels tend to be one piece and stronger. I like bases on my WW2 stuff as it helps with transport and storage.