Most of the time that will depend on the carrier. You can remove most of the Samsung apps like S Note, etc., but the carrier puts its own bloat in there. But 25% is about normal. (Some phones have used 50% of the available space for the system.)
But I'd suggest that you freeze or turn off anything you don't want first. Then if it causes problems, you can just unfreeze it. If you uninstall it, you might not be able to get it to reinstall it.
Rukbat, my tab is a Wifi-only Tab, which means there is no carrier involved. Great idea to freeze first before uninstalling. I could also use Titanium Backup app to get a copy of everything on my device and store on my computer.