They are very similar, which can be a bit confusing. You are correct that chunk persistence is mainly for console to keep the save file size smaller, though you can use it for the same thing on PC. In most cases, it can probably just be left at unlimited on PC, though. Chunk reset time is only for PC (I believe) and its purpose is mainly to reset areas to the original state so that you can loot stuff again and fill in terrain and fix broken things and so on. It's mostly valuable for servers so areas that aren't visited can get reset back to the original state so people can loot the areas again instead of everything already being looted by the time a new player joins the server.
These two settings do have a similar effect... they both decrease save file sizes if setting the values lower, and they both "clean up" the chunks when resetting them. Also, they can interact with one another... if you set persistence low and chunk reset high, the chunks can end up resetting before the chunk reset timer's time gets triggered.
Now, this next part is a guess on my part and I don't know if it's accurate. I *believe* that chunk persistence will reset any chunks that are older, even if they have been visited recently, while I know for sure that the chunk reset timer only resets chunks that haven't been visited within that timer's amount of time (if it's set to 10 days and you visit in on day 9, the timer resets and it'll be another 10 days before it could get reset based on the timer). So if the first part is correct, it means that if you want chunks to reset even in regularly visited areas, you may want to set chunk persistence lower because the chunk reset timer may never reset those chunks that are visited regularly.
In both cases, chunks won't reset within land claim areas or near bedrolls. I think chunks with vehicles also don't reset, but don't quote me on that.
