The starter set PVC models can be painted to a standard where they make passable game pieces, but as said there's just no comparison to the resin models.
Purely from a quality point they're less terrible models and more entirely unsuited to the material. PVC works fine for Star Wars Legion with large, friendly, somewhat heroically scaled models that don't have fine detail. For the same reason, the Super Mutants in the starter set look superior to the humans, and there's nothing wrong with the even larger Deathclaw. The problem the Super Mutants suffer is while cloth and mountains of muscle work fine in PVC, the finer detail of their faces is not captured on the models. Modiphius's choice of realistic proportions is simply not compatible with the material.
By contrast the resin models are very much superb, sporting fantastically fine detail and in my opinion they are very much worth getting, and if the decision is between resin or PVC, I'd choose resin without a second thought.
One thing to consider is that you very likely want the starter set for the cards and dice (and obviously the rule books won't hurt). Wasteland Warfare is built around the cards and many basic cards are found in the starter set and (I think) nowhere else. Now getting the rules for equipment is easy by downloading the PDFs from Modiphius's website, but if you want to build a loot deck to draw from in settlement mode or during games, it will obviously be beneficial to have the cards so you can mix them with cards from other boxes to make a random loot deck (same goes for events and all the other
RPG elements that make narrative mode fun.
You definitely need the dice to play, and having the cardboard markers isn't a bad idea. Combined with the cards and the nice Deathclaw model I don't think you need to feel bad buying it at 50% off. In that case I'd consider the subpar PVC models a bonus that will give you pre-assembled models for a quick start into the game.
One last point, I don't know about your skill level or interest in painting, but as said the resin models have very fine detail. Having thematically fitting PVC models to practice painting on and get in the right frame of mind can be beneficial if you come from larger, more heroically proportioned models like
GW's.
Here's my painted starter set for reference. I'd say the worst models of the group are the Settlers which have a few details which I had to look up on the resin models to figure out what I was actually painting, and Nora who I painted after the resin model so I instantly became very well aware of the difference in detail quality.