The "plus" is all in how the DM describes it; as a metagame issue it's irrelevant to how the item "actually works" in the "real world" of the game. A Cloak of Resistance is easily explained as being an item that provides a small amount of anti-magic, or helps the wearer's willpower oppose various dangers and "just magically" get luckier or tougher or stronger-willed... in other words, it does just what its name suggests, it lets the wearer "resist" dangerous things. This is no more out-of-place in a world where magic works, than a sword which "just magically" allows you to cut things better, or penetrate hides you couldn't penetrate with a mundane weapon.
Usually when I'm describing the effects of an item to my players, I explicitly state that although I'm going to use game mechanics to describe the effects so the players know what the item does, that is not how the characters themselves understand the item to work. The information the characters get is in some terms relating to them and their "real world" which is our game setting, and in translating what the characters hear to our world they become transformed into game mechanics and rules. That's how I always do it- and sure, it breaks the fourth wall briefly, but sometimes you just have to get on with the game. It's better to do things that way than to try coming up with some gobbledygook/technobabble jargon to translate the game mechanics into every time I need to give the result of an Analyze Dweomer, and have the players re-translate what I said back into game mechanics in their own minds.