I still think there is an underlying difference, which is often difficult to explain due to common terminology.
Arminians would claim that prevenient Grace was given to everyone as a result of what our Lord Jesus Christ did for us - but that the prevenient Grace is what gives us the ability to choose to follow God. Orthodox believe that ability to choose was never taken away from us. We still are born in God's image, albeit a marred image. That said, we cannot achieve theosis without God's Grace. So yes, I think the key differences is what we mean by a "corrupted image".
I believe that both Calvinists and Arminians teach, against Pelagianism and semi-Pelagianism, that the sinner’s will is depraved and bound to sin, so it can't respond positively to God without supernatural grace. Armenians believe God's prevenient Grace is given to all before we choose to accept or deny salvation, whereas Calvinists (correct me if I'm wrong) believe that God's Grace is extended to the elect specifically.
So how does Orthodoxy fit in? We also reject Pelagianism. That said - prevenient Grace is kind of redundant. We never lost God's Grace (I'm not referring to sanctifying Grace here though). Because we didn't lose His Grace, we are able to choose His sanctifying Grace (offered through Christ's work of salvation), which allows us to participate with God (synergism) to be sanctified or to grow closer to theosis, and ultimately to have eternal life.
Honestly, I'm probably botching this explanation
The nuances are difficult to describe at times.