Certainly.
The 1.4 was much more expensive while the 1.8 was the usual kit lens included with the lower priced OM's (10/20/30/40). Most OM2's came with the 1.4 when they first came out. I'm sure there are 4 times as many 1.8's than 1.4's
It has 7 elements versus 6 in the 1.8 (early Zuikos were designated as "F-Zuiko" or "G-Zuiko" where the letter represented the number of lens elements). The 1.8 is built a little lighter internally as well.
The 1.8 has 6 aperture blades whereas the 1.4 has 8. The iris on the 1.4 produces a more pleasing bokeh, especially with high contrast highlights such as sun shining through tree leaves. The 1.8 has very nice out-of-focus blur, almost as good as the 1.4, but with busy backgrounds the bokeh is sometimes slightly nervous.
The 50/1.8 is considered sharper than the 1.4 but I don't see that. I do think the 1.8 has better contrast - maybe due to internal reflections and the smaller elements.
The "silver-nose" versions were single coated and the "black-nose", later production, had multi coatings. I typically use a lens hood which cuts out a lot of flare and increases contrast on either lens. With a hood you don't need the multi coatings. At night you can put away the hood.
Shot into the sun I think the 1.8 has a nicer flare pattern where the 1.4 makes better silhouettes.
I like the glow of the silver-nosed 1.4 and it's my most used Zuiko.
-Bill