I'm still yet to get any of them to download. =( But i would like to know also. I just purchased the engine so now I'm stuck and don't know what to do.
Let me share what I learned from ChezJfrey and my gaming experience.
Gentlemen Of Forturn (GOF) series, including 1.2, 2.0, 2.5, ERAS2 are based on City Of Abandoned Ship (COAS), which was developed by Storm2.8 engine. So the interface, main quest lines, most of factors are the same as COAS. ERAS has more historical ships and characters, and be continully updated through 2023. So ERAS II is the newest in the series.
New Horizons (NH), is based on the Pirates of The Caribbean (POTC), which was developed by Storm 2.0 engine. So the interface, characters are different from COAS.
I have downloaded and played both. To me, I like ERAS2 more, the interface and control are more familiar since COAS is newer than POTC. Moreover, the historical factors in ERAS2 are amazing.
So, try and play what you like.