Shield of magic resistance

I found a couple of times these new shields of magic resistance. I was wondering how they actually resist magic like slow or striking spells. Is it a percentage reduction? Are elemental spells considered magic, effectively making the shield a resist all? And also, how much resistance it provides compared to other items like rings or cloaks?

I currently have a nice shield of electricity resistance and am hesitant to swap it for one of magic resistance. I remember in my last playthrough I was badly damaged by a lightning spell while wielding a shield of magic resistance (can't remember how much it was enchanted, though), so I figured it provided less resistance, but for a wider range of sources.

Any insight would be much appreciated!

Sorry for the late reply. Shields of magic resistance actually only grant resistance to magic damage (for example wands of striking, or the "magic missile" spells dark mages will blast you with), not against all magic spells. Thus it can be useful against mages, but you will also need a source of resistance to other elements.

I would like to have Willpower grant you a general saving throw against all magic one day.

Thanks for the data. I think the name is somewhat misleading, though, as lightning and fire spells are still magic.

About willpower, how would that stat train? I'm not very fond of a chance of negating all damage or effects from spells, honestly. I'd rather prefer effect magnitude or duration reduction, maybe in the form of a percentage range to make it less predictable (say each spell effect is reduced between 15-25% for instance). It makes more sense and is more reliable than an all or nothing approach, which I believe also comes from the need to simplify calculations in pen and paper games.