I'd argue that GDIShrink is less likely to introduce compatibility issues than RebuildGDI, but I wouldn't redo all of your library anyways. You should be totally fine for 99% of games with RebuildGDI, just replace those that have problems for GDIShrinked ones. The main advantage of GDIShrink over RebuildGDI, for the 99% of games that work with both, is that GDIShrink doesn't need to extract the files from the dump, it can copy to the sdcard and shrink on the fly. This should save time. It also keeps the filesystem basically untouched compared with the original, which isn't necessary but is cleaner IMO and helps compatibility.