DE-2 user here. I like the slightly bigger magnification of the DE-2, the lower profile and lower weight.
All these combined, and the fact that I do not wear glasses and hike a lot with the F3 as film camera in my bag make the choice easy on me. Often the F3 with DE-3 just does not fit in the bag anymore where the F3 with DE-2 just fits.
Since my DE-2 is slightly beaten up (even lower profile for less space in the bag) I usually mount the DE-3 when I take pictures OF the F3. But in all honesty, it's a camera to take photos with.
On my F and F2 I use the eye level/DE-1 finders, again to save space and weight when out in the field.