Going back on this, I know it’s old...
I like to keep my PSX ROMs aligned to the Redump DATs which means .BIN and .CUE files. Also, I’ve found that converting them to .PBP has thrown errors in the past. Not looked into .CHD files but with both these methods of converting ROMs it can be a pain if you have a large collection.
Since this was posted I still use an unzip script but I use .M3U files for multi-disc games (which seem to use a single .BIN and .CUE in Redump terms) and .CUE for single disc games (which Redump seems to either use single .BIN or multiple .BINs).
This method has both storage benefits and save game benefits as the save files are aligned with the .M3U for multi-disc games.
PS. Last time I checked the entire PSX Redump collection was 3.7TB so there are benefits to unzipping into a cache if storage is tight and you’re not doing so to an SD card.