Vampires can rest in broad daylight and survive the experience
On OpenMW v0.35 vampires can rest in broad daylight without taking any damage. Attempting the same in vanilla Morrowind would kill the unholy creature that you are.
(RM-2399 from redmine: created on 2015-02-23 by Sergey "Shnatsel" Davidoff, , closed on 2016-07-06 by Miroslav Remák, relates #1996 (closed))