That won't do squat for a vanilla record being deleted,
That's the best use for using Ignore. You don't delete the actual vanilla record, you just tell the game to disregard it. The record still exists inside the Oblivion.esm file. By using Ignore, you're removing all trace of your change to the vanilla entry and allowing it to come through from the default esm again.
and if you're deleting something you added that has a formID belonging to the mod, deleting it is entirely clean. No stray bits get left behind from that.
I've seen plenty of references in the details list of records that have a D beside their name, meaning they had been deleted in the CS but some trace of them still remained in the esp. Using Ignore will eliminate them completely. After fighting with the delete function several times in mods I've worked with, and still having those entries appear in the CS, I stopped using it altogether and simply set them to Ignore when I load the mod. It's a bit more work yes, but it's 100% guarenteed to get rid of something you don't want. Using Delete isn't. Most of the time yes, but not always.