This.Just don't get a flat one. You want a little dome.
The key to a good Comet is one with dome. Get one that is flat on top and it's going to be squirrely. Get one with good dome and it will be amazing. Plastics are amazingly unimportant in Comets, one with good dome in any plastic flies like a good Comet. Getting one that flattens out on top in any plastic is going to leave you with a disc that sometimes flies like a good Comet and sometimes doesn't, leaving you perplexed and unhappy.
As for trying out a Comet, X is cheaper and they fly like good Comets when they have good dome so why not? Just make sure it has dome. Just say no to flat Comets.