Not to continue to steer this towards a plastic vs plastic battle, but it has been my experience , and from what I've read , that for a given disc the DX is the least stable, the Star is more stable than DX , and Champion is the most stable.
Champion plastic lasts the longest/takes the longest before it changes flight, Star is second, DX changes/gets beat up the quickest.
Champion plastic is awesome with regard to it's longevity. I lost a few Champs years ago that I had used for years, if I still had them I bet they would still be in good shape.
My advice to a beginner would be get a low-to-mid weight (160g or so) Mako or Mako3 . Play with that disc exclusively for at least a season. You will learn alot , and you won't get confused by switching from disc to disc.
Both of those discs are extremely neutral and are not too high of a speed rating for new players. This means you will be able to throw them like they were meant to be thrown, and any variation from a straight flight is due to how YOU are throwing the disc, not some inherent characteristic of the disc.
Discs that have inherent curve/turn tendencies make it hard for beginners because they teach you to rely on the disc rather than learn how to throw the right way.
For example, when I first started playing I had a friend that used a DX Stingray. He soon was able to outdrive the group we played with. Once other people started using fairway drivers and were able to throw as far or further than he did, he tried throwing a fairway driver ( I forget what it was , a Teebird or Banshee I think) . He could throw his Stingray much further . His tendency to count on the Stingray's Hi Speed Turn (lack of stability/unstable disc) totally screwed him up when he tried to go to a longer range , more stable disc.
Sure, had we known better, he could have used a Cheetah, or some other unstable fairway driver and achieved better results, but that's not the point. The point is he learned a bad habit from using a disc that naturally flew anhyzer and throwing it with hyzer netted a result of a mild S curve . Sure, it worked for him in the beginning, but in the end he gave up playing disc golf , I think mainly due to ignorance and poor original habits.
Just my $0.02
DX Birdie 175g, Opto Pure 170g. Champ Cobra 165g, Star Mako 162g, Champ TL 168g, Medium Trak 157g, VIP Sword 175g, Medium Lace 163g, RHBH , RHFH , RHOH/Tomahawk