Just some general info: Evince and Okular (the successor to kpdf) both use poppler under the hood (which is maintained/released by the Okular maintainer), so their performance and behavior will be somewhat similar, though you can make a difference at the app level with things like tiled rendering and smarter prefetching. I'm not on top of how the two compare there, though. Okular also has pluggable backends and there's an in-development mupdf backend around.