Have ’em both. Use ’em both. Love ’em both.
But, they are VERY different cameras, for very different purposes. Here are some of my observations about the differences and similarities between the two cameras, and also some of what I have found to be weaknesses in both. Keep in mind that the way you use your camera, and what you shoot, will mean that you may well not agree with my comments. Using a camera to make photographs is a very personal experience and one size does not fit all.
Olympus OM-D EM-1 Mk II with Zuiko 40-150mm f/2.8 lens.
The original Olympus OM-D EM-1 with Zuiko 7-14mm f/2.8 lens
(L) Original Olympus EM-1 (with 7-14mm f/2.8 Zuiko lens) and (R) Olympus OM-D EM-1 Mk II (with Zuiko 14-40 mm f/2.8 lens)
(L to R) Olympus OM-D EM 1, Olympus OM-D EM-1 Mk II, and Nikon D850 with Sigma Art 24-70mm f/2.8