VSFilter is a newer form of Direct VobSub:
If you already have VobSub 2.23, just install VS Filter. You don't have to uninstall VobSub.
If you don't have VobSub, just install VS Filter. You don't have to install VobSub 2.23.
If you have VS Filter 2.26 or older, update it to 2.27 or newer.