There was some speed up with a more recent loader, one you may or may not be using.
You can also do things to help the speeds on the older ones. The main issue seems to be it loads the file table and fiddles with it, reduce the size of that (clear out the saver folder, put games in directories, if you do not need to wander around with the entire set or something close to it then don't....). A decent SD may help but the bulk of any slowdown is unrelated to ?SD speed.