According to Asus product comparison
(link):
The "Plus" is black.
The "Plus" has "All High-quality Conductive Polymer Capacitors".
The "Plus" has TPM support.
The "E" has smaller vCore: Adjustable CPU voltage increments.
(probably dependant on BIOS so shouldn't be a factor)
Identical other than that.
But I'm sure you already checked the manufacturer website!