Avoid plastic press dies?

[linux]

I've been doing some research trying to decide which "good" press to buy and the choices come with either no dies or various collections of dies, sizes and materials.  I recall seeing a couple of posts where users recommended staying away from plastic/delrin dies and I wonder if people have had bad experiences with them.  I guess the alternative is aluminum.  (I don't know much about the bakelite dies but I think they are the domed ones used for acrylic domed crystals.)

[Malocchio]

The sets of four are identical except that one is made of plastic and the other probably brass. The plastic ones feel like they bend when installing tension ring crystals so I prefer the metal ones a lot. The press itself is nice too, very heavy cast iron frame.