These are the major differences between the MSI Z270 Gaming Pro Carbon and the Asus ROG Strix Z270E:
MSI supports 8 different RAM speeds (up to 3800MHz) | Asus supports 13 different RAM speeds (up to 3866MHz)
MSI has HDMI and DVI-D on-board graphics output | Asus has HDMI, DVI-D and DisplayPort outputs
MSI has 3x PCIe x16 and 3x PCIe x1 slots | Asus has 3x PCIe x16 and 4x PCIe x1 slots
MSI has no built-in Wi-Fi or Bluetooth | Asus has built-in Wi-Fi and Bluetooth wireless connectivity
MSI has 1x on-board RGB LED connector | Asus has 2x on-board RGB LED connectors
MSI has only 2x on-board USB2.0 headers | Asus has 3x on-board USB2.0 headers
MSI has 2x on-board USB3.0 headers | Asus has only 1x on-board USB3.0 header
MSI has no on-board USB3.1 header | Asus has 1x on-board USB3.1 header
MSI has 2x USB2.0 rear panel ports | Asus has no USB2.0 rear panel port
Asus has other specialty on-board connectors (3D Mount, CPU OV, COM, T_Sensor, EXT_FAN, etc.)
Specs-for-specs and feature-wise, the Asus ROG Strix Z270E is the better motherboard between the two.