Defualt Warcraft vs ElvUI Interface - What's Better?

For year's I have used and loved ElvUI as a complete UI replacement for Warcraft, however, heading into The War Within I have made a massive house clean for many of my Weak Auras and addons which lead me to wonder - what exactly does ElvUI do for me that I need, and could the default UI work just as well with less problems?

Addons mentioned in this video:
iLevel - https://www.curseforge.com/wow/addons/ilevel
ElvUI - https://tukui.org/elvui
Vuhdo - https://www.curseforge.com/wow/addons/vuhdo