I'm under the impression with the polycarbonate lens the UV treating is a must and the cut and polish isn't worth doing unless you plan on doing the UV coating as well
If you refinish polycarbonate and leave it bare, it will oxidise super quickly. You can prolong that with waxes and sealants and even quartz and ceramic coatings - but they will still oxidise in time. 2K clear is a
really good option to use but there is the downside of having to deal with the texture from the gun, sanding and polishing it all out and then protecting it from there once cured. Also, unless you're doing it yourself, it's really only worth doing to factory HID lights that tend to cost $900+ each to replace. Not worth doing to holden lights that can come in at under $300 a pair.
The factory coating is purely UV protection - it has little chemical resistance or hydrophobic properties or anything like that. But it's quite thick (generally around 12-15 microns) and is cured under direct UV light. You can then apply quartz or ceramic coatings over this UV layer to then work to protect that and help it last beyond it's normal durability or you can wax/seal it when you do the rest of the car. Because it's designed specifically for the job of protecting raw polycarbonate, the lens will not oxidise under the coating - the only way it will haze is if the UV coating becomes compromised through neglect or damage. And it is significantly cheaper than prep and labour for 2k clear, though is a very different process to normal sanding and polishing. Also, due to it needing to be cured under a UV light rig, it isn't really a DIY job.
