Thanks, good food for thought. A lot of what CEDAR does is pretty old, but there are still some things that have yet to be matched by other products, e.g. phase correction of mono groove walls, fixing lathe errors for 100 year old recordings, some more sophisticated EQ correction, and even some of the 78-specific crackle reduction. At a glance, SweetVinyl seems good for vinyl, but shellac is a whole different animal. In my experience, any vinyl product designed without shellac in mind will either absolutely murder shellac or be totally useless.
I agree that correcting for cartridge is probably small potatoes and almost not worth considering when dealing with shellac, but I'm still curious to hear the differences. Part of the reason is also wanting to have a library of ruler-flat transfers and not someday regretting that I could have done them better.
The Shure V15Vx is about as good as it gets for 78s. Must-haves for any cartridge include swappable stylii and cantilevers that can take at least 5 grams of tracking force. You need at minimum 6 different stylii to be able to get best results. Groove widths vary widely.