This isn't really a Simple Question, nor is it a Simple Answer, but rather a statement.
There currently exists a bias on Geekhack when it comes to keycaps. That bias is towards PBT, the thicker the better, and away from thin ABS. Thick ABS is somewhere in the middle of the spectrum.
However, just like with switch preference, the type of keycaps you prefer is just that, a personal preference. Just because one person loves thick PBT, doesn't mean it is the best, nor does it mean that YOU will like it best. I personally prefer thick ABS from Cherry/GMK the best, but I don't mind thin ABS from SP at all. I certainly prefer them to the super-textured PBT that is common, and feels slippery to my fingers.
So, just because a group of people have decided that thick PBT is the "best," doesn't necessarily make it so. I think some of it is the "bandwagon" effect. Certainly some of it is because ABS does tend to develop a shine, i.e. lose its texture, with use, which some people find distasteful.
But the main point of my rambling is that, just like BlueBär and CPTBadAss expressed, you should try different keycap sets and decide from your actual experience which is better, to you. Don't just take someone's word for it. I could tell you that 65g linear MX switches are the "best," but they may not be the best for you, and you may prefer 67g clicky MX, pink Alps, capacitive buckling springs, or even 55g Topre.
That is the wonderful thing about this point in time. There exists a multitude of options when it comes to keyboards and their accessories, and you have many choices you can make when purchasing these items. We have demonstrated to manufacturers that there is a market for these things, and we will support their products if they continue to innovate and improve. Also, if something doesn't exist yet, or isn't readily available, we make things ourselves. That, to me, is the fun part of this hobby.
Try new things. Make decisions based on your experiences. Enjoy your feeling! of oneness with cup rubber! Live long, and prosper!