For PVE, magicka has typically been stronger. Impale and Merciless Resolve are better morphs than the stamina version, because they cause more damage and Disease doesn't do much in PVE.
PVP is a hybrid model. There are about 3 variations that work between gank, tank, and standard burst damage.
Magblade is my preference in PVE. Better damage dealing options. More versatility with Impale than Killer's Blade, even though Killer's Blade has a larger execute window (50%) and a heal, being in melee range is problematic unless you are tanking.
The Shadowy Disguise and Concealed Weapon combo hit like a truck, and having a deep magicka pool for Shadowy Disguise aids in positioning in harder fights in group content where you may not be able to flank effectively without dropping aggro.
Plus being able to quickly slip into the healer role is crucial for my playstyle.
Just my opinion.
Tybalt Kaine Khajiit Nightblade Aldmeri Dominion
PC/NA
Guildmaster- Lucky Raven
Knight of Marrow - Blackfeather Academy
Adepti- The Witches Goblet
"Nightblade healer huh? How does that work?"
"I drain the blood of our enemies and fire it into you. It's a lot less messy than it sounds, and yeah I'm basically a Vampire without the whole AGH FIRE BAD"